METAPHYSICS

Physics is the scientific investigation of the fundamental nature of physical being. Metaphysics—at least within that tradition that traces itself back to Aristotle's eponymous treatise—is the philosophical investigation of the even more fundamental nature of being as such. Metaphysics is concerned with the contours of the categories of entity postulated or presupposed by any possible, acceptable, account of the world, whether of the physical world or of any other aspect of the world. The task of metaphysics is to lay out a complete, coherent ontology, embracing all that is necessary to capture the correct account of the world in any of the special inquiries—whether they be empirical, mathematical, modal, or moral.

The Changing Methods of Metaphysics

Traditionally, metaphysics was practiced as a top-down, a priori discipline, with Euclidean geometry as its model. The metaphysician begins with self-evident principles of a highly general nature, together with appropriate definitions, and proceeds to draw out the necessary consequences.

This approach is clearly exemplified in the work of two prominent eighteenth-century metaphysicians, Gottfried Wilhelm Leibniz and Benedict (Baruch) de Spinoza. Leibniz spun metaphysical gold out of the dross of the principles of noncontradiction and sufficient reason: His entire Monadology (1965), replete with an infinite collection of possible worlds, with the actual world (the best of all possible worlds) consisting of a myriad of mutually reflecting, simple, mind-like substances. Spinoza was even more self-consciously imitating Euclid, but his conclusions are almost diametrically opposed to those of Leibniz. Spinoza's ontology comprises exactly one substance (God-or-Nature), of which the mental and the physical realms are two aspects, and everything about the one Substance is absolutely necessary—only the actual is really possible.

In the light of its lofty aim, the conflicting conclusions of its practitioners, and their exaggerated claims to have achieved the aim with completeness and certainty, it is perhaps unsurprising that the discipline of metaphysics, so practiced, has been regularly contested. Empiricists, led by David Hume, have often attacked a priori metaphysics, contrasting its lackluster or conflicting results with the astonishing successes of empirical sciences, on the one hand, and of mathematics on the other.

At the end of the eighteenth century, Immanuel Kant, in response to Hume's critique, attempted a partial vindication of a priori metaphysics. According to Kant, metaphysics can play a legitimate role as handmaid to science and a less straightforward role in upholding ethics. Through an analysis of the cognitive needs of thinking, sensing beings, it can establish the presuppositions of Newtonianism—Euclidean space, absolute time, deterministic causation, and enduring interacting substances obeying conservation laws. In addition, if a metaphysical hypothesis—the existence of God or the freedom of the will—is required for the smooth and effective operation of morality, then that may be legitimately adopted as though it were true, as a postulate of practical rationality. Kant's compromise evidently failed to rein in the metaphysical spirit, his work unleashing a century's worth of metaphysical system-building in an increasingly problematic idealist tradition.

In the late nineteenth century, the appetite for idealist metaphysics began to fade. A realist assault on this tradition was launched by Alexius Meinong, Bertrand Russell, Gottlob Frege, and George Moore, and their style of argumentation, as much as the content of their conclusions, was influential in shaping the twentieth century's more circumspect approach to metaphysics. Rather more radically a group of scientifically minded thinkers—inspired by Ludwig Wittgenstein's Tractatus (1922), rallying under the banner of Logical Positivism and brandishing a verificationist criterion of meaning—declared all metaphysical discourse completely meaningless. They argued that sentences that cannot be either verified by observation or proven by pure logic and are not merely beyond our knowing but are strictly speaking, meaningless. Echoing Hume, they denied any legitimate space for metaphysics between a posteriori science and a priori logic. The shortcomings of Logical Positivism were rapidly exposed (mostly by its adherents and fellow empiricists such as Karl Popper), but its offspring—ordinary language philosophy—cast over the metaphysical enterprise a pall that did not lift until the 1960s. Metaphysics, cautiously revived by heirs of both movements (albeit with notable differences in methodology detailed below), is once again a flourishing discipline in the early twenty-first century.

Contemporary metaphysics is characterized by a bottom-up approach rather than the traditional top-down approach. The contemporary metaphysician begins with a problem or puzzle, often generated by some basic data or the consequences of such data. The different sources of this basic data characterize two broad traditions. One tradition—championed by Moore, mediated midcentury by philosophers such as P. F. Strawson, Arthur Prior, and Roderick Chisholm and embraced by contemporary philosophers such as Frank Jackson—takes as prime data the deliverances of everyday discourse and commonsense, so called "Moorean facts": for example, that I have two hands; that there is a piece of cheese in my left hand and a stick of chalk in my right; that the chalk and the cheese are distinct things; that cheese and chalk have the same color, and so on.

A different tradition, traceable back through the empiricists (such as Russell and Rudolph Carnap), mediated by Willard Quine, and embraced by philosophers such as John Smart, John Mackie, and David Armstrong, is less impressed with commonsense data. It takes the serious data to be constituted by the presuppositions and deliverances of extraordinarily successful scientific theories: that there is no role for the flow of time in a fundamental account of the world; that the fundamental laws are probabilistic rather than deterministic; that simultaneity is relative to motion; and that space–time may be non-Euclidean. The presuppositions and deliverances of the mathematical disciplines essential to science are also treated as serious data: for example, that there numbers, and an infinite class of such; that there are functions from numbers to numbers and that the infinite class of such functions is vastly bigger than the infinite class of numbers; that there can be no complete axiomatization of mathematical truth, and so on.

The two traditions overlap, of course, as exemplified in the work of prominent metaphysicians like David Lewis. Lewis (1981, 1986) draws extensively on both kinds of data, seeking an ontology compatible with and explanatory of both. However, if that's not possible, the data from the sciences usually trump those of commonsense.

To say that contemporary metaphysics is bottom-up is not to saddle it with a crude inductivism—the fallacious inference of general theories from finite data. The task of the contemporary metaphysician is not so much to prove an ontology, either from high-level first principles or from lower-level data, as to propose an ontology to accommodate and explain the data, to resolve apparent conflicts by explaining away the appearance of such, or explain why the data are misleading. The methodology is less like that of pure mathematics and more like that of science—conjecture and refutation—with the difference being the kind of data that require accommodation or furnish a counterexample.

Given a finite amount of data, the number of potentially adequate metaphysical theories seems limited only by the imagination of practicing metaphysicians. To decide between theories we need more than data accommodation. Metaphysicians typically subscribe to Occam's Razor —the injunction to refrain from multiplying entities beyond necessity. The Razor, read as an endorsement of ontological abstemiousness, is sometimes considered a license to slash entities without regard for a complementary principle—the injunction to refrain from eliminating entities that are necessary. Necessary for what? For accommodating and explaining the data. The upshot of these two principles is, then, that a theory must explain the data; and, of two theories that both explain the data, the theory with fewer ontic commitments is to be preferred.

So, we begin with a domain of discourse—such as mind, or mathematics, or morality—and note that, on the surface at least, it supplies data that posit or presuppose an ontology. Our ordinary mind-talk, for example, presupposes mental states (experiences, thoughts, desires, emotions) along with physical states, and a rich network of causal interactions between them. Mathematics posits numbers, classes, functions, spaces, and a rich array of other abstract objects. Morality presupposes goods and evils, rights and obligations, virtues and vices. But there is often a problem with the entities posited or presupposed. For example, if the mind is something over and above the physical, how can it causally interact with the physical without violating physical laws? And if it is difficult to understand how the mind could affect physical states, it is even more difficult to see how numbers, existing outside space and time, could affect the mind. Whence, then, our knowledge of numbers? Finally, a good would have to be something the mere recognition of which would engage the will, and nothing (some will aver) could do that. The question arises, then, whether such things as minds, numbers, and goods should be counted among the indispensable building blocks of the universe. Is it coherent to postulate them? Are they consistent with the rest of what we know? And even if it is coherent, do we really need them to accommodate the data? Can they be explained, or explained away, in a complete, consistent account of the world? Already with the posing of such seemingly unavoidable questions, the enterprise of metaphysics is up and running.

A Spectrum of Metaphysical Approaches

Whenever entities are posited to explain the data provided by some domain of discourse, three broad responses, differing in ontological commitment, are possible. At one end of the spectrum we have realism, at the other, antirealism ; between, we have determinationism. Each can be divided into two subcategories.

The realist with respect to a domain accepts both the discourse and the data at face value; affirms the necessity of the entities postulated to explain the data, and adds that the entities really are basic—they are additional to (or "over and above") whatever else there may be. Realism comes in two broad varieties. Transcendent realism locates the posited entities outside the spatiotemporal, causal order. By contrast, immanent realism locates the entities within the spatiotemporal, causal order, typically ascribing them an indispensable causal role.

Most realists about numbers and other abstract entities have been of the transcendent variety, but recently, some number-realists have embraced immanence, espousing a role for abstract entities in the causal network. A transcendent realist theory of value is also usually ascribed to Plato—with the Form of the Good, like all the Forms, eternal and unchanging, existing "over and above" the transient realm of particular contingent beings. It is not hard to find naturalist theories of value that ascribe them a causal role, but as we will see below, there is an important sense in which naturalism about value is not fully realist—it does not posit value "over and above" the natural realm. A version of immanent value realism holds, like Platonic realism, that value is real, that it is something "over and above" the purely natural realm, but adds that value plays a causal role with respect to the motivational states of sensitive beings.

At the other end of the spectrum we have antirealism. The antirealist repudiates the entities in question, maintaining that the discourse that delivers the data is fundamentally misleading. But the data can be misleading in one of two very different ways. The data are recorded and delivered in what appear to be genuine, truth-bearing (or assertoric) claims. What masquerades as truth-bearing claims, however, might really be something else, and the nonassertoric antirealist says just that. Rather than being truth-bearing assertions, they might be expressions of desire, or moves in a language game, or instruments in the derivation of genuinely truth-bearing assertions. In ethics, nonassertoric antirealism is noncognitivism ; in the philosophy of science, instrumentalism ; in the philosophy of math, formalism ; in the philosophy of mind, the intentional stance theory ; and so on. Nonassertoric antirealism allows apparent reference to the purported entities while denying there are any such.

The assertoric antirealist, by contrast, accepts that the discourse consists of genuine truth-bearing assertions but rejects those assertions as untrue. In the metaphysics of the mind, this constitutes eliminativism concerning the entities. In the metaphysics of morality, it is known as the error theory. An increasingly popular variant of assertoric antirealism, especially with respect to abstract entities such as numbers, is fictionalism. The fictionalist thinks that the relevant claims are untrue but also thinks that there is a point in continuing the discourse just as though they were.

Between realism and antirealism lie a collection of approaches that share a doctrine of determination. Like the realist, the determinationist acknowledges the discourse and the data that suggest the disputed entities. Like the antirealist, however, the determinationist denies that the disputed entities are basic, holding that the truth about the higher level is fully determined by the truth about ontologically more fundamental entities. Determinationism also comes in two varieties, reductive and nonreductive. The reductionist holds either that the disputed entities are reducible to more basic entities (entity reduction) or that all the facts about the disputed entities are reducible to facts about undisputed entities (fact reduction).

A necessary and sufficient condition for entity education is that the (apparently) higher-level entities are identical to lower-level entities, that properties of the reducible entities are identical to properties of the lower-level entities, and consequently that truths about the reducible entities turn out to be truths about the entities to which they reduce. The reduced entities are nothing but the lower-level entities to which they are reduced. Thus, for example, logicism claims that numbers are reducible to classes: The number zero, for example, is simply identical to the empty class; the number one is identical to the class of all singleton classes, and so on. The identity theory of the mind claims that mental states are identical to physical states of the brain. The ethical naturalist claims that moral properties (such as the rightness of actions) are identical to natural properties (such as maximizing expected happiness).

A classic example of reduction without entity reduction can be found in Russell's justly famous theory of descriptions. In his Principles of Mathematics, Russell embraced Meinong's theory of nonexistent objects: that there are genuine objects—possibilia like the golden mountain and the King of France, and impossibilia like the round square—which have a range of features (the golden mountain is made of gold) but which lack the crucial feature of existence. In "On Denoting"—which set the tone for twentieth century analytic philosophy—Russell repudiated this ontology by showing that phrases that apparently denote such possibilia are not really denoting phrases at all. They do not denote particulars, and they do not denote anything else. Russell shows us a way of dispensing with nonexistent objects, but unlike the eliminativist, he does not repudiate the data or the discourse that suggest them. Rather, he shows how to translate the data into facts about properties. Nonexistents disappear from Russell's ontology theory, but the data that suggested them are fully accommodated. This is a kind of reduction without being a reduction of the problematic entities. It is a reduction of the facts about the purported entities while the entities are repudiated or "analyzed away." Let's reserve the term fact reduction for those cases in which every fact about some purported entities is equivalent to a fact about some other entities; there is no entity reduction, and the purported entities are repudiated.

Finally, we have nonreductive determinationism, which has gained considerable currency through the notion of supervenience in philosophy of mind. All determination theories affirm that there can be no difference in one kind of entity without a difference in another, more basic kind. For example, a widely held view is that there can be no difference in the moral without some difference in the natural. Another is that there can be no difference in the mental without some difference in the physical. The higher-level entities are thus determined by the lower-level entities. What is characteristic of a supervenience theory as such is that it posits this determination, does not repudiate the higher-level entities, but also denies the reducibility of the higher-level entities to the lower-level entities.

Supervenience is naturally located between reductionism and realism. The supervenience theorist agrees with the realist and the fact reductionist that the higher-level entities cannot be reduced to the lower-level entities but agrees with the entity reductionist that the higher-level entities are not ontologically basic. There is thus a sense (weaker than the reductionist sense) in which supervening entities are "nothing over and above" the basic entities, but there is also a sense in which the supervening entities, while falling short of the independently real, enjoy some kind of autonomy denied reducible entities.

Those sympathetic to physicalism (viz., there is nothing over and above the physical) but skeptical that mental state kinds are identical to physical state kinds are attracted to the thesis of the nonreductive supervenience of the mental. Those sympathetic to naturalism (viz., there is nothing over and above the purely natural) but skeptical that moral properties are identical to natural properties are attracted to the nonreductive supervenience of the moral on the natural.

Supervenience theories share considerable common ground with emergence theories—lately enjoying something of a revival—and it is interesting that supervenience is popular in domains (such as philosophy of mind and philosophy of biology) where emergence theories also seem a promising compromise between realism and reductionism.

Whether or not there is logical space for nonreductive determinationism has not yet been satisfactorily settled. Like other attempts to forge middle paths between two clear alternatives, a supervenience theory embodies a certain instability, suggesting to some that, in the end, the supervenience advocate will either be forced to embrace the reductionism eschewed or lapse into a form of realism.

One particularly important determination theory is worth singling out for special attention since it has played a pivotal role in the history of metaphysics—namely, determination by the mental (or mind-dependence ). Broadly speaking, this is idealism, and it is a perennially attractive option—indeed, so attractive that idealism has often been taken to be the rival to realism. Bishop George Berkeley famously claimed that physical objects are nothing but (are identical to) congeries of experiences. The notorious problem of maintaining the intermittently observed tree in the quad in uninterrupted existence led Berkeley to posit an omniobserver, someone to keep a perpetual eye on things. A different response to this problem moves beyond actual experiences to various potential experiences. Physical differences that go undetected may be detectable by observers under suitable hypothetical conditions. (If you were in the quad, or having in-the-quad experiences, then you would have tree experiences.) An idealist could add those conditional states to the determination base. This move, from Berkeleian idealism to phenomenalism, might be a move from entity reduction to fact reduction, or it might be a move from entity reduction to supervenience. If physical objects "disappear" in the final analysis leaving behind the truths that appear to be about them, then we have fact reduction. If physical objects are not identified with anything else, reference to physical objects as genuine entities remains, and the totality of facts about such objects is determined by the actual and conditional facts about experiences, then we have a version of supervenience.

Faced with the fact that actual minds have various cognitive shortcomings, the idealist may also want to tidy up both actual and potential mental states in various ways. The physical facts are held to be determined not by the actual mental states of existing observers but by the mental states that ideal observers would have if they were ideally placed. Hence, variations on the basic idealist theme of mind dependence include positivism, ideal limit theories of truth, and related accounts such as internal realism. Many who regard Berkeleian idealism about the physical world as deeply implausible have embraced some version of idealism in other domains—with respect to mathematical entities, theoretical entities, God, possibilities, colors, values, and universals. This three-fold classification helps explain why there is a certain amount of confusion in debates about realism since antirealism and nonrealism (the disjunction of antirealism and determinationism) and are not usually defined or carefully distinguished.

A Problem in Metaphysics: Universals and Particulars

These patterns of opposition and compromise—realism versus antirealism, with determination seeking a middle way—have played out across the metaphysical spectrum. They find a particularly clear expression, however, in a problem of central concern to metaphysics since its very inception—the problem of universals and particulars, a problem the intrinsic interest of which proves prefatory to its myriad applications. For one's attitude toward universals and particulars has profound implications for one's attitude to a host of other problems—those of abstract entities, change, time, causation, identity, possibility, value, and morality.

Consider a stick of chalk (A ), a wedge of cheese (B ), and a chunk of chocolate (C ). A is chalk and B is not chalk—it follows that A and B are not identical. This is an application the principle of the indiscernibility of identicals, often associated with Leibniz: If entity X is identical to entity Y, then anything true of X is also true of Y. This in turn is a consequence of the principle of non contradiction : that no proposition can be both true and false. So much seems straightforward, yet this sort of easy observation intersects with a second, equally obvious fact, to create a puzzle: A is yellow and B is yellow. How can A and B, clearly distinct, be the same —that is, yellow? How can they be both the same and not the same? That's puzzling.

Whenever we strike an apparent contradiction (A and B are the same and are not the same), it is natural to make a distinction. A and B are not numerically the same (they are two) but they are qualitatively the same (they instantiate the property yellowness ). Properties are instantiated by particulars one at a time—they are monadic universals. But there are also universals that characterize couples and triples. Resemblance, for example, is not a property that particulars have or lack. Resemblance involves pairs—it is a dyadic relation. And betweenness, which characterizes triples, is a triadic relation, and so on. The problematic data can be accommodated, and the apparent inconsistency explained away, by an ontology that posits two radically different categories of being—particulars and universals—and a relation of instantiation (itself a universal) holding between particulars and universals.

Responses to this two-tiered ontology have traditionally been categorized as either nominalist or realist, with a third category—conceptualist —sometimes thrown rather awkwardly into the mix. The six-fold schema set out above suggests that the space of possibilities is much richer. With respect to universals, one might be antirealist (assertoric or nonassertoric), determinationist (reductive or nonreductive), or realist (transcendent or immanent). Further, any of those positions might be combined with one of the six distinct approaches to particulars. So in all there are thirty-six possible combinations, not just two or three. For example, one might be a transcendent realist about both universals and particulars, or an immanent realist about one and a reductionist about the other, or a reductionist about both universals and particulars (invoking some third category of entity to which both reduce), and so on. Not all of these combinations have been embraced, but many have. For the purposes of illustrating the approaches and the arguments that characterize them, a few of the more commonly held positions are sketched.

Realism about Particulars, Nonrealism about Universals

A particular, unlike a universal, lacks the mysterious capacity to be "fully present" in distinct particulars. We feel we understand particulars, perhaps because we are experientially acquainted with them. We do seem to be acquainted with concrete particulars—such as bits of chalk, cheese, and chocolate. But there are other purported entities that strike us as particular rather than universal that are not like these—for example, numbers, classes, propositions, and possibilities. And there are others that are difficult to categorize—such as space and time.

Particularism embraces realism about particulars—there are particulars, and particulars are not reducible to anything more basic—and adds that the only basic entities are particulars. It is thus a one-tier ontology with both considerable simplicity and commonsense in its favor. Particularism affirms that anything at all (universals, numbers, classes, possibilities, causation, space, time) is either eliminable or reducible to particulars. Concrete particularism is more austere, restricting fundamental being to concrete particulars, the paradigms of which are physical objects. The concrete particularist is a realist about concrete particulars and is typically an immanent realist, assigning particulars both spatiotemporal location and a role in the causal order. There are versions of transcendent realism about particulars although typically transcendent particulars will be abstract rather than concrete (for example, numbers, classes, and possibilities).

In what follows particularism is combined with five different versions of nonrealism about universals. These five accounts have all been called "nominalisms," but the nomenclature is not particularly perspicuous. Sometimes nominalism connotes concrete particularism ; at others, the broader doctrine of particularism. Sometimes it connotes antirealism about universals; at others, determinationism. Predicate nominalism, which holds that there are just particulars and the words (names) we call them by, is perhaps the clearest candidate for the title. Mereological nominalism combines concrete particularism with reduction of universals. Conceptualism, sometimes called "concept nominalism," is a version of idealism—reduction of universals to mental particulars. Extensionalism, sometimes called "class nominalism," is a reduction of universals not to concrete particulars but to classes of concrete particulars. Finally, resemblance theories are determinationist and may be of either the reductive or nonreductive kind. The determination base includes concrete particulars and resemblances between them.

predicate nominalism as an eliminativist particularism

The most austere version of nominalism—often called word or predicate nominalism —is naturally construed as concrete particularism combined with eliminativism about universals. It holds that there are concrete particulars and there are the predicates (words) we apply to them, and that is all. Simply put: Things are yellow because we call them "yellow." We call things by the same name—A and B are both called "yellow"—but there is no need to postulate a universal of yellowness instantiated by all things so called. (Distinct people are called "Brian," but we do not postulate a universal Brianness.)

The predicate nominalist repudiates universals rather than reducing them to particulars but accommodates the data by means of the following equivalences:

A is yellow ⇔ A is called "yellow."

B is yellow ⇔ B is called "yellow."

C is brown ⇔ C is called "brown."

On the left-hand side we have some Moorean facts, which apparently presuppose concrete particulars (A, B, C ) and universals (yellowness; brownness). However, the right-hand side supplants reference to a property with reference to a predicate. Since it is implausible to identify yellowness with the predicate "yellow," the position is plausibly construed as denying the universal yellowness: There is a word "yellow," we call a bunch of things "yellow," and if we call them "yellow," they are yellow (end of story).

Some criticisms of word nominalism are worth sketching because they involve argument kinds that crop up repeatedly in this area. The word nominalist's explanation of the data seems backwards. Distinct things are not made yellow by virtue of being called "yellow;" they are called "yellow" because they are one color, conventionally dubbed "yellow." If we call a person "Brian," then for any other similar person—for example, his identical twin—it is a matter of separate convention whether we also call him "Brian." But if we call a color sample on a chart "yellow," and another sample is qualitatively indistinguishable from that, the original convention covers the second color sample, and we call it "yellow," too.

Secondly, since there are only concrete particulars, words must also be concrete particulars. How many words are there on the following line?

yellow, yellow

There are two answers: two and one. There are two concrete words but only one dictionary entry at issue. We must distinguish between word-tokens and word-types. On the one hand, word-tokens are spatially located, unrepeatable, concrete particulars. A word-type, on the other hand, has distinct word-tokens as instances. Word-types look very like universals. Elimination of one universal—yellowness—has only been achieved at the cost of accepting another—the word-type "yellow."

To eliminate this word-type, the nominalist might deploy the complex predicate "called 'tokens of the word-type "yellow."'" But this launches a regress, for the same problem resurfaces for applications of this new predicate. Universals are eliminated at one level only to have them pop up in the shape of word-types at the next. Only if word-types at all levels are eliminable in favor of word-tokens will universals be exorcised, but that would require an infinite supply of word-tokens, and there are just not enough to go around. The nominalist might invoke possible word-tokens here, but that would launch the nominalist beyond the actual world into the problematic outer space of possibility—not a happy place for nominalists to venture.

Finally, chalk is called "yellow," but the cheese is also called "yellow." Calling involves many distinct particular-word pairs—it seems to be a dyadic relation linking particulars and word-tokens, and relations are universals. If one tries to eliminate this relation in favor of another word, we are again launched on a tiresome regress.

There is an alternative construal of predicate nominalism according to which yellowness is eliminated in favor of a different property—being called "yellow." But this would be neither elimination of universals (since both properties have an equal claim to being universals) nor a reduction of universals to particulars. It is simply a proposal to economize within the class of universals itself. As Lewis noted in a different context (possibility), it is not just the number of entities that fall within an ontological category that matters to ontic simplicity, but more importantly, it is the number of basic ontological categories countenanced. If there is something unsatisfactory about the category of universal, then whether you admit one, or a million, or an infinite array is immaterial—your attempt to eliminate universals fails.

mereological nominalism as entity reduction

Predicate nominalism is an eliminativist version of concrete particularism, but there are reductionist versions too—mereological nominalism, for example. Mereology is the theory of the part–whole relation. Some particulars are parts of other particulars. The top of the pen and the body of the pen are both proper parts of the pen, and the pen is the mereological sum of the body and the top. The pen continues to exist even when the top is removed and its parts are separated. Perhaps the chalk and the cheese are also parts of a particular, a spatially scattered whole made partly of chalk and partly of cheese.

Starting with A, B, and C, there are at least four such distinct, albeit overlapping, mereological sums—(A +B ), (B +C ), (A +C ) and (A +B +C )—yielding at least seven distinct concrete particulars in total. Note that sameness of parts entails sameness of whole: ((A +B )+A ), for example, has just two parts, A and B, and so is identical to (A +B ). If there are n basic (nonoverlapping) concrete particulars, then, assuming the principle of unrestricted mereological composition (that every sum of concrete particulars is itself a concrete particular), there are 2ⁿ —1 concrete particulars. The principle is controversial, but one way of characterizing concrete particularism is this: The principle of unrestricted composition places an upper bound on the collection of entities.

Let S (F ) be the mereological sum of all particulars to which predicate F applies—S (yellow) is the sum of all yellow things. Plausibly, something is yellow if and only if it is a part of S (yellow). This suggests the following analysis:

X is F ⇔ X is a part of S (F )

Note that the analysis assumes that for any predicate F, the sum of all things with F is also a concrete particular. However, it does not assume unrestricted composition—for there may be collections of particulars to which no single predicate applies. This mereological analysis, if adequate, might allow us to identify the property F -ness with S (F ), a concrete particular.

Mereological nominalism accommodates quite a lot of data about properties such as water and yellow. But take two related properties such as water and single H₂O molecule that involve the part–whole relation—a quantity of water has parts that are single H₂O molecules. Mereological particularism entails that for something to be water, it has to be a part of S (water), and for something to be a single H₂O molecule, it has to be part of the S (single H₂O molecule). But these two sums are identical —sum all quantities of water, and sum all single molecules of water, and you arrive at the same whole. So mereological nominalism entails that to be water just is to be a single molecule of water—and that, unfortunately for the theory, is just false.

conceptualism as idealism about universals

The attraction of conceptualism is that it reduces universals to something concrete, particular, and also mind-friendly: concepts. Concepts are things that the mind can get a handle on whereas universals may be problematic in that respect. The beginning idea is that the cheese is yellow if and only if the cheese falls under the concept of yellow. Quite generally, where C (F ) is the concept of F, we have:

X is F ⇔ X falls under C (F ).

We can thus explain the data by appealing to a concept—an apparently familiar mental particular—rather than a mind-independent universal.

Our mental vocabulary (such as belief, thought, desire) suffers a pervasive state-content ambiguity. My belief that the cheese is yellow might be my state of believing, as in: "My belief that the cheese is yellow, given my aversion to yellow cheese, made me refuse it." But it might also be the content of my belief, as in: "My belief is just the same as yours: that the cheese is yellow." Our believings are distinct entities, but what we believe here is the same. Believings are mind-dependent (which believings there are depends on who believes what), but the common content of distinct believings does not depend on what you or I believe.

Concepts also suffer the state-content ambiguity—there are concept-graspings and there are the concepts grasped. Concepts in the state-sense are mind-dependent (which concept-graspings exist depends on who is grasping what), but the contents of such graspings do not appear to be mind-dependent.

The conceptualist may eschew concepts as contents of graspings in favor of a myriad different and individual graspings. But your grasping of yellow has something in common with mine. What is that? If we apply conceptualism to this datum then, as with predicate nominalism, we are launched on a regress and there will not be enough particular concept graspings to accommodate all the data.

extensionalism: reduction of universals to classes

For every predicate F that may or may not apply to a particular, there is the class of all and only the particulars to which F applies in fact, the extension of F —E (F ). In our example, class {A,B } is the extension of yellow, {C } the extension of brown. Something is yellow if and only if it is in the class of yellow things. So the following is an apparently necessary equivalence:

X is F ⇔ X is a member of E (F ).

This suggests identifying F -ness with its extension, E (F ). (After abandoning concrete particularism, Quine adopted extensionalism.)

Extensionalism is sometimes called "class nominalism," but the postulation of classes marks a real departure from concrete particularism. Classes may be particular, but they are not concrete. Classes are "over and above" the concrete particulars that are their members, and Nelson Goodman's criterion explains why. Starting with A, B, C there are at most seven concrete particulars. However, there are many more classes. There are seven nonempty classes of particulars. Each one pairs off with a mereological sum—{A,B } with A +B, {A } with A, and so on—but we cannot identify these classes with the corresponding concrete particulars. Classes are individuated by membership: They are identical if and only if they have exactly the same members (the principle of extensionality). So the singleton class {A } is a distinct entity from its sole member A. A piece of cheese is not a class consisting of a piece of cheese. Quite generally a class is not the mereological sum of its members.

Once we acknowledge classes of classes, the hierarchy of classes "over and above" the concrete particulars, A, B, C explodes into a vast and infinitely intricate structure, one massively exceeding the modest seven-member ontology of mereological sums countenanced by the concrete particularist. The two-membered class {{A,B },A }, for example, is distinct from the two-membered class {A,B }. The former has a member {A,B } that the latter lacks. Contrast this with ((A +B )+A ) and (A +B )—the same concrete particular.

Extensionalism, a radical departure from nominalism, thus has plenty of resources—but does it have enough to do justice to the data? Being a chordate is the property of being a heart-bearing animal; being a renate, the property of being a kidney-bearing animal. These are distinct properties. As it happens, these two properties have the same extension. Extensionalism thus entails that they are one and the same property. As generous as the ontology of classes is, it is not generous enough. This coextension problem is a classic example of an argument against a reduction thesis. The reduction base is shown to be insufficiently rich to capture all relevant entities.

A different criticism suggests that there are too many classes as well. A universal involves sameness. There are, however, "arbitrary" collections of concrete particulars exhibiting no genuine sameness. If the sameness of A and B (yellowness) reduces to the fact that both are members of {A,B }, why does not the fact that A and C are both members of {A,C } yield a genuine sameness there? The class theorist could bite this bullet and accept that all classes are universals. (Bullet-biting is a rather common response to recalcitrant data.) A different response would be to block the counterexample by declaring that only certain "natural" classes are genuine or have what it takes to be universals. (This response exhibits an ad hocness that is arguably worse than bullet-biting.)

An explanatory asymmetry argument against extensionalism is often deployed. It is claimed that A 's being yellow explains A 's membership of the class of yellow particulars, not the other way around. This claim contradicts the extensionalist's claim that these facts are really one and the same. The extensionality principle, however, entails that if X is a member of a class C, then that very class could not have lacked X —any class C * that lacks X is necessarily distinct from C. That A is a member of {A,B } is necessary. That A is yellow is, by contrast, contingent. No contingent fact explains a necessary fact, and so the argument fails. Even though it fails, it suggests a different argument. It follows, by the indiscernibility of identicals, that a contingent fact (such as A 's being yellow) cannot be a necessary fact (such as A 's being a member of {A.B }). But extensionalism entails they are the same fact. Call this the necessary extension problem.

The coextension and necessary extension problems are closely related. The reason chordate and renate cannot be identified with the class that is their common extension is that their extensions might well have differed from each other. And that presupposes that they have their extensions contingently, not necessarily. Since chordate and renate differ in their possible extensions, one way of modifying extensionalism would be to expand the reduction base to include possibilia. Two accounts have predominated. One embraces possible but nonactual particulars and takes the extension of property P to be the class of actual and nonactual particulars that have P. (This presupposes that particulars are world-bound—no particular appears in more than one possible world.) Another is to include possible but nonactual worlds with common or overlapping domains of particulars. In each possible world W, the property P has an extension in W. The property P thus induces a function F (P ) from worlds to extensions—and a reductionist might identify P with the function F (P ). These accounts are both reductionist, presupposing different accounts of possibility. They go well beyond the domain of concrete particulars entertained by traditional extensionalists, and they are both known as intensional accounts of universals.

Despite the richness of the framework of worlds and functions, however, it may still not be rich enough to capture all the data. Being triangular is the property of being a plane figure with three angles. Being trilateral is the property of being a plane figure with three sides. Because each logically necessitates the other, these properties induce the very same function from worlds to classes of concrete particulars (or classes of possibilia), and so even these intensionalist accounts render them identical. If they are not identical, then we need something more discriminating than functions from worlds to classes of particulars with which to identify them.

resemblance theories: reduction and supervenience

An important group of theories claim that property facts are determined by facts about resemblance. A crude version of the resemblance theory invokes paradigms, and resemblance to such paradigms—namely, where P (F ) is a specified paradigm of F :

X is F ⇔ X resembles P (F ).

The shortcomings of the paradigm account are numerous. It entails, for example, that the designated paradigm of yellowness is necessarily yellow (since everything necessarily resembles itself). It also entails that anything resembling P (F ) in any respect at all is F. A far more promising account draws on the notion of similarity circle —a class such that all the members of the class resemble every member of the class, and nothing outside the class also resembles every member of the class. Provided that there is sufficient variety in particulars, similarity circles carve out what are, intuitively, the genuine universals without the necessity for privileging any particular. This might be regarded as a reduction of universals to classes of particulars plus resemblances, but it can also be regarded as a supervenience thesis: Properties supervene on a basis consisting of resemblance and the domain of particulars. There can be no difference in properties without some difference in the structure of resemblances—same resemblance structure, same properties.

As Russell famously noted, any account that grounds properties in resemblance faces a problem. Resemblance is a relation between particulars and as such seems to be a universal. It might be considered an ontological saving to reduce myriad universals to one, but as noted in the context of word nominalism, what is important is the number of nonempty ontological categories.

This criticism of resemblance theories can be generalized to any attempt to reduce universals to something "else." Suppose we reduce property P to some entity Reduct(P ): the class of P s; the mereological sum of P s; the concept of P ; the similarity circle that corresponds to P, and so on. The reductionist says that for X to be P is for X to bear some suitable relation R to Reduct(P ). But the reductionist is then forced either to admit one universal—the relation R —or to apply the theory to R itself, launching an unhappy regress.

Resemblance theorists might employ the tu quoque, charging that the realist faces a similar regress. Assume realism: For X to be yellow is for X to instantiate (I ) the universal yellowness (Y ). But then, for X to instantiate Y is for a certain triple—X,Y,I —to stand in a relation, I *. I * cannot be I. For one thing I, is a dyadic relation, and I * is a triadic relation. For another, this would involve a relation taking itself as one of its own relata. So I * is distinct from I. We can repeat the argument to obtain a third relation I **, and so on. So the realist is thus as much involved in a regress as any of the reductionist rivals.

The realist might appeal to the category response: The regress is damaging to the particularist because it shows that the category of relation cannot be done away with. That's an internal inconsistency. But the realist about universals does not object to that category being nonempty, and even an infinite class of distinct instantiation relations constitutes no embarrassment for realism as such. Of course, a realist who wants to keep the number of universals down to a small or finite collection might be embarrassed.

Finally, the resemblance theorist may run out of the kind of variety in actual objects required to set properties apart. (Renate and chordate are still coextensive.) To increase the variety and block a coextension objection, the resemblance theorist might take a now familiar tack—embracing relations of resemblance between possible as well as actual particulars. As with the related attempts to deflect counterexamples by invoking possibilia, this constitutes a significant and not entirely unproblematic expansion of the reduction base. Certainly it violates the original nominalistic spirit that inspired it.

Realism about Both Particulars and Universals

One explanation for this apparent failure to eliminate or reduce universals is realism—that universals are neither eliminable, nor reducible, nor supervenient. That this is no proof of realism is obvious—we may not have exhausted all possible alternatives. However, realism about universals conjoined with realism about particulars does explain these failures, as well as providing an explanation of the ubiquitous Moorean facts of predication.

transcendent realism about universals

What is often called ante rem realism, or Platonic realism, is a transcendent realism: that irreducible universals exist of necessity, beyond contingency in general, and beyond the contingent causal network in particular. One powerful explanatory principle, typically embraced by transcendent realists (Plato perhaps) states that any meaningful predicate, whether simple or complex, applies to things in virtue of designating a genuine universal. So not only contingent predicates such as "black" and "raven" designate universals, so, too, do predicates that apply of necessity (such as "self-identical"); predicates that apply to nothing (such as "unicorn"); predicates that apply to nothing of necessity (such as "self-distinct"); and finally, not only simple predicates (such as "black" and "raven") designate universals, but so do complex predicates (such as "black raven," "not black," "black or raven," "black if and only if a raven," and so on). Since predicates apply to universals themselves (e.g., yellowness is a pretty color ), universals are instances of other universals. This unrestricted transcendent realism makes the domain of universals a largely a priori affair.

Perhaps the greatest threat to unrestricted transcendent realism is Russell's paradox. Particulars have properties (such as being honest or cowardly), but properties also have properties (honesty is virtue, chalkiness is a universal, a piece of chalk is not a universal), and those properties have properties in turn (virtue is good, being a universal is something all universals have in common, being a particular is a universal not a particular).

By unrestricted realism the two predicates—being a universal and being a concrete particular —designate two universals, U and P. All universals have U in common. U is a universal, and so U itself has U. U is self-predicating. However, P is not a concrete particular (it is a universal), and so P is non-self-predicating. Given unrestricted realism, the meaningful predicate non-self-predicating designates a universal, N. Each universal either has N or lacks N. If N has N, then N is non-self-predicating—but then N does not self-predicate and so N lacks N (contradiction). If N lacks N, then N is not non-self-predicating; that is, N is self-predicating, and so N has N (contradiction again).

Russellian paradoxes can be constructed for just about any account of universals, including the most austere version of predicate nominalism. (The predicate "short" is called "short," but the predicate "long" is not called "long." Call the former "self-predicating" and the latter "non-self-predicating." Is the predicate "non-self-predicating" called "non-self-predicating"? Paradox ensues.) Russellian paradoxes are thus too pervasive, the realist might claim, for them to be peculiarly damaging to realism. Still, short of embracing paradoxes, the realist has an obligation to deflect them.

Any adequate realist answer to Russellian paradoxes must involve some restriction on the predicates: namely, not every apparently meaningful predicate necessarily designates a universal. Russell's theory of types is a classic restriction. Type theory stratifies entities. Simplifying somewhat: particulars are type-0 entities, properties of particulars are type-1 entities, properties of (type-1) properties are type-2 entities, and so on. A type-0 entity may either have or lack a type-1 property, and a type-1 property may have or lack a type-2 property, but no property either has or lacks a property of the same type. A property is always one type higher than the highest type of entity to which it can be sensibly applied or denied. Thus, the question of whether a universal P has or lacks itself does not arise. It is neither true nor untrue that P lacks P. The very attempt to apply P to itself is a category error (like the attempt to apply the color green to the number 7), and so the predicates "self-predicating" and "non-self-predicating" are literally meaningless. (The notion of a category error took on a life of its own long after Russell's theory of types lost the attention of most philosophers.) The paradox is blocked because there are no universals of self-predication or of non-self-predication.

The chief worry about a type theory is that it rules itself out as unsayable—to state it one must violate its strictures. Take the claim no universal can be applied to, or denied of, a universal of the same type. This makes a perfectly general claim about all universals. What type does the universal of being a universal (U ) belong to? It cannot consistently be assigned a level. It is this problem that undergirds the famous theme of Wittgenstein's Tractatus, that philosophy consists of things that can be shown but cannot be said.

immanent realism about universals

An important group of restricted realist theories trace their ancestry to Aristotle. Not every predicate picks out a universal, and it is a contingent matter, to be settled a posteriori, what universals there are. In rebus realism is a version of immanent realism. It begins with the simple idea that universals exist only in their instances. If a universal is not instantiated, it does not exist. Consequently, a predicate must apply to a particular for it to designate a genuine universal. This instantiation condition prohibits universals such as unicornhood. It also rules out various truth-functional combinations of universals. Even if black and raven are both universals, the predicate "not black and a raven" does not designate a universal (since all ravens are black).

Armstrong, a prominent advocate of immanent realism, places two further conditions on a predicate for it to designate a universal. Firstly, the predicate must apply in virtue of a genuine identity in the particulars. Even if yellow and raven are both universals, the disjunctive predicate "yellow or a raven" does not pick out a universal, despite being instantiated, because there is no qualitative identity exemplified by a yellow submarine and a black raven. Secondly, Armstrong draws on a condition inspired by the Eleatic Stranger in Plato's Sophist, who makes the intriguing suggestion (known as the Eleatic Principle ) that the mark of being is causal power. Armstrong requires that to be real, a universal must feature in causal laws. (Universals must do some work for their living.)

The Eleatic Principle gives natural science a crucial role in delineating the ultimate constituents of being. Interestingly, it also suggests an immanent realism that denies the instantiation condition. Michael Tooley has argued, within the same immanent realist framework, that there could be properties that play a genuine role in the causal order, because they enter into basic causal laws, but that could remain uninstantiated. If causal power is the mark of the real, it would be hard to deny them ontic standing, but if so, they are not in rebus universals—they exist independently of their exemplification by particulars. Clearly, there is wide scope for other, quite different versions of both transcendent and immanent realism about universals.

Realism about Universals, Reductionism about Particulars

If one embraces realism about universals, then, for the sake of simplicity, it would be worthwhile exploring the reduction or particulars to universals. Every particular X comes along with a bundle (or a class) of properties, B (X )—the class of all the properties it has. Further, an object X has property P if and only if P is a member of B (X ). This suggests that we embrace just one entity (the bundle) rather than two (the particular and its bundle). The bundle theory identifies a particular with the bundle of its properties.

This bundle theory faces problems analogous to the reduction of universals to classes of particulars—both too many classes and not enough classes. Firstly, there are too many classes. The class {golden, mountain} does not pick out any actual concrete particular—the golden mountain does not exist. This fact, however, may not be considered entirely undesirable. Meinong famously argued that metaphysics needs to accommodate data pertaining to the nonactual as well as to the actual. To explain the nonexistence of the golden mountain, the golden mountain must be an object with a specific nature, a nature that it possesses of necessity. If being golden and mountainous were contingent properties of the golden mountain, then who is to say that Kilimanjaro is not the golden mountain? The bundle theory thus dovetails nicely with this theory of possible objects.

The bundle theorist still owes us an account of the distinction between concrete existent particulars (Kilimanjaro) and merely possible particulars (the golden mountain). Meinong thought that it is their completeness that sets them apart. Kilimanjaro is complete—for every property, Kilimanjaro either has it or lacks it. The golden mountain is incomplete—it is a mountain, and it is made of gold, but for many properties (e.g., more than 1 mile high ), it neither has the property nor lacks it. But this will not do—we could specify complete bundles of properties that do not correspond to any concrete particular.

Are there enough bundles of properties to accommodate all particulars, or does the bundle theory face a coextension problem? A bundle theory of particulars entails the Identity of indiscernibles (the converse of the indiscernibility of identicals): If X and Y are qualitatively identical (share all properties), then X and Y are numerically identical. This principle would be trivially true provided conditions such as being identical to X were genuine properties. But the bundle theorist cannot start with properties that presuppose antecedently given particulars. The bundling properties would have to be purely qualitative. But then it does seem possible for distinct particulars to share all their purely qualitative properties. (Quantum theory, for example, entails that it is possible for two bosons to share their fundamental quantum states—including the state corresponding to location.) That is incompatible with the bundle theory.

An essential property of a particular is a property without which that particular would not exist. It is controversial whether there are essential properties, and if so, which properties of any given particular are essential. However, there is widespread agreement that not every property of a particular is essential to it. At least some properties are such that an item could lose them without going out of existence. The bundle theory suffers an analogue of the necessary extension problem. Classes by their nature are necessary, eternal, and unchanging. So the bundle theory would appear to entail super-essentialism : that every property of a particular is essential to it; that if a particular lost a property, it would cease to be.

Rejecting Realism about Universals and Particulars

The space of possibilities is not restricted to reduction in one of two directions. Universals and particulars might both be reduced to some third, more basic, kind of entity. One prominent example of such an approach is trope theory.

A trope (this patch of brownness, that instance of sweetness) is a particularized universal—a particular instantiation of a universal by a particular. Put like that, of course, tropes apparently presuppose both particulars and universals. They appear to be nonbasic entities. But it is a characteristic move in metaphysics to take as ontologically basic something that has hitherto been assumed to be derivative and reverse the ontological order.

Tropes have the advantage of incorporating both particularity and qualitative character in their nature and are thus promising building blocks. The proposal is that particulars and universals are both classes of tropes, albeit different kinds of classes: Particulars are classes of co-located tropes—tropes occupying the same space and time—and universals are classes of exactly resembling tropes. A particular X has property P just in case the class of co-located tropes that make up X overlaps with the class of resembling tropes that constitute P.

Trope theory has the advantages of simplicity and comprehensiveness. Further, it avoids the co-extension problem that besets extensionalism. No redness trope is identical to a roundness trope. So even if redness and roundness always go together (they are always co-located) the class of all roundness tropes is a distinct class from that of redness tropes.

Trope theory retains the necessary extension problem. Classes have their members by necessity, but a concrete particular does not have its properties by necessity. By identifying predication with the intersection of two classes, trope theory implies that all predications are necessary. Again, such problems may be avoidable by invoking possible worlds, but only at the cost of expanding the reduction base to something that makes the resulting reduction rather costly in terms of ontological resources.

The Future of Metaphysics

The proposed schema for locating metaphysical theories is applicable in all of the various domains of the discipline, and the argument patterns for realism, antirealism, and determinationism bear important similarities across those domains. The basic data might involve claims about time, causation, possibility, the fundamental truths of arithmetic, mental states, spatial relations, value, morality, and so on. Theorists will take the data and lay out an ontology to explain them, or explain them away, either taking the surface ontology at face value, explaining it in terms of something more basic, or occasionally eliminating it altogether.

The modern metaphysician, aware of the underdetermination of theory by data, rarely expects or demands that the arguments conclusively establish any metaphysical proposal. Rather, the metaphysician will examine each metaphysical proposal on its explanatory merits, assessing first its explanatory adequacy with respect to the existing data, searching for new data to test and probe the proposal, and then turning to the more inherently contestable issues of theoretical elegance, economy, and overall coherence with other metaphysical theories. Inevitably, a considerable degree of fallibility and uncertainty remains. Still, that acknowledged, the future of metaphysics is no less secure than the future of science: Human beings can and will continue to probe the fundamental nature of the world right up to the limits of their cognitive abilities. Their doing so will, inescapably, implicate them in the enterprise of metaphysics.

See also Aristotle; Armstrong, David M.; Berkeley, George; Carnap, Rudolf; Chisholm, Roderick; Frege, Gottlob; Gödel, Kurt; Goodman, Nelson; Hume, David; Kant, Immanuel; Leibniz, Gottfried Wilhelm; Lewis, David; Mackie, John Leslie; Meinong, Alexius; Metaphysics, History of; Metaphysics, Nature of; Moore, George Edward; Newton, Isaac; Plato; Popper, Karl Raimund; Prior, Arthur Norman; Quine, Willard Van Orman; Russell, Bertrand Arthur William; Smart, John Jamieson Carswell; Spinoza, Benedict (Baruch) de; Strawson, Peter Frederick; Wittgenstein, Ludwig Josef Johann.

The Encyclopedia contains two additional general articles on this subject: Metaphysics, History of , and Metaphysics, Nature of . It also features the following articles: Absolute, The ; Apeiron/Peras ; Appearance and Reality ; Arche ; Being ; Categories ; Causation: Metaphysical Issues ; Chance ; Chaos Theory ; Continuity ; Cosmos ; Determinism, A Historical Survey ; Dialectic ; Emanationism ; Essence and Existence ; Eternal Return ; Eternity ; Hen/Polla ; Idealism ; Identity ; Infinity in Theology and Metaphysics ; Logos ; Macrocosm and Microcosm ; Materialism ; Monad and Monadology ; Monism and Pluralism ; Naturalism ; Nature, Philosophical Ideas of ; Nomos and Phusis ; Nothing ; Nous ; Ontology ; Panpsychism ; Personal Identity ; Personalism ; Persons ; Pessimism and Optimism ; Possibility ; Relations, Internal and External ; Solipsism ; Substance and Attribute ; Time ; Unconscious ; Universals, A Historical Survey ; Vitalism ; Voluntarism ; Why .

Differing schools of metaphysical thought are represented in the articles Aristotelianism ; Augustinianism ; Cartesianism ; Hegelianism ; Neoplatonism ; Ockhamism ; Platonism and the Platonic Tradition ; Scotism ; Spinozism ; Stoicism ; Thomism .

Bibliography

Aristotle. "Metaphysics." In The Complete Works of Aristotle: The Revised Oxford Translation, edited by J. Barnes, 1552–1728. Princeton, NJ: Princeton University Press, 1984.

Armstrong, D. M. A Theory of Universals. Cambridge, U.K.: Cambridge University Press, 1978.

Ayer, A. J. Language, Truth, and Logic. New York: Oxford University Press, 1936.

Berkeley, G. Three Dialogues Between Hylas and Philonous. Oxford: Oxford University Press, 1998.

Bradley, F. H. Appearance and Reality. London: Swan Sonnenschein, 1893.

Brentano, F. Psychology from an Empirical Standpoint, edited by O. Kraus. Translated by A. C. Rancurello, D. B. Terrell, and L. L. McAlister. London: Routledge, 1973.

Carnap, R. Der Logische Aufbau der Welt. Leipzig: Felix Meiner Verlag, 1928.

Carnap, R. Meaning and Necessity. Chicago: University of Chicago Press, 1947.

Carnap, R. "The Elimination of Metaphysics through Logical Analysis of Language." In Logical Empiricism at its Peak: Schlick, Carnap, and Neurath, edited by S. Sarkar, 10–33. New York: Garland, 1996.

Chisholm, R. M. Person and Object: A Metaphysical Study. La Salle: Open Court, 1976.

Churchland, P. M. "Eliminative Materialism and the Propositional Attitudes." Journal of Philosophy 78 (1981): 67–90.

Davidson, D. "Mental Events." In Experience and Theory, edited by L. Foster and J. W. Swanson, 79–101. London: Duckworth, 1970.

Dennett, D. C. The Intentional Stance. Cambridge, MA: MIT Press, 1987.

Duhem, P. M. M. The Aim and Structure of Physical Theory. Translated by P. Wiener. Princeton, NJ: Princeton University Press, 1954.

Feyerabend, P. "Mental Events and the Brain." Journal of Philosophy 40 (1963): 295–296.

Field, H. H. Science without Numbers: A Defence of Nominalism. Oxford: Blackwell, 1980.

Gödel, K. "Some Basic Theorems on the Foundations of Mathematics and Their Philosophical Implications." In Collected Works. Vol. III, edited by S. Feferman, et al., 304–323. Oxford: Oxford University Press, 1995.

Goodman, N. "A World of Individuals." In The Problem of Universals, edited by I. M. Bochenski, A. Church, and N. Goodman, 13–32. Notre Dame, IN: University of Notre Dame Press, 1956.

Goodman, N. "Predicates Without Properties." Midwest Studies in Philosophy 2 (1977): 212–213.

Hegel, G. W. F. Phenomenology of Spirit. Translated by A. V. Miller, Oxford: Oxford University Press, 1977.

Jackson, F. From Metaphysics to Ethics. Oxford: Oxford University Press, 1997.

Kant, I. Prolegomena to Any Future Metaphysics. Translated by L. W. Beck. Indianapolis: Bobbs-Merrill, 1950.

Kim, J. Supervenience and Mind: Selected Philosophical Essays. New York: Cambridge University Press, 1993.

Leibniz, G. W. Monadology. In Monadology and Other Philosophical Essays. Translated by P. Schrecker and A. M. Schrecker. New York: Bobbs-Merrill, 1965.

Lewis, D. On the Plurality of Worlds. Oxford: Blackwell, 1986.

Lewis, D. Parts of Classes. Oxford: Blackwell, 1991.

Mackie, J. L. Ethics: Inventing Right and Wrong. Harmondsworth, NY: Penguin, 1977.

Maddy, P. Realism in Mathematics. Oxford: Oxford University Press, 1990.

Meinong, A. "On the Theory of Objects." In Realism and the Background of Phenomenology, edited by R. Chisholm, 76–117. Glencoe, IL: Free Press, 1960.

Montague, R. Formal Philosophy: Selected Papers of Richard Montague. New Haven, CT: Yale University Press, 1974.

Moore, G. E. Philosophical Studies. New York: Harcourt, Brace, 1922.

Oddie, G. Value, Reality, and Desire. Oxford: Oxford University Press, 2005.

Parsons, T. Nonexistent Objects. New Haven, CT: Yale University Press, 1980.

Plato. The Dialogues of Plato. Translated and edited by B. Jowett. Oxford: Clarendon Press, 1953.

Popper, K. Conjectures and Refutations: The Growth of Scientific Knowledge. London: Routledge, 1963.

Post, J. F. The Faces of Existence: An Essay in Nonreductive Metaphysics. Ithaca: Cornell University Press, 1987.

Priest, G. Beyond the Limits of Thought. Oxford: Clarendon Press, 2002.

Prior, A. N. Papers on Time and Tense. Oxford: Clarendon Press, 1968.

Putnam, H. Reason, Truth and History. Cambridge, U.K.: Cambridge University Press, 1981.

Quine, W. v. O. From a Logical Point of View. Cambridge, MA: Harvard University Press, 1953.

Rodriguez-Pereyra, G. Resemblance Nominalism: A Solution to the Problem of Universals. Oxford: Oxford University Press, 2002.

Ryle, G. The Concept of Mind. London: Hutchinson's University Library, 1949.

Russell, B. "On Denoting." Mind 14 (1905): 479–493.

Russell, B. The Principles of Mathematics. Cambridge, U.K.: Cambridge University Press, 1903.

Russell, B. The Analysis of Matter. London: Routledge, 1927.

Schlick, M. "Form and Content: An Introduction to Philosophical Thinking." Moritz Schlick: Philosophical Papers. Vol. II, edited by H. L. Mulder and B. F. B. van de Velde-Schlick. Translated by P. Heath. Dordrecht: Reidel, 1979.

Smart, J. J. C. Philosophy and Scientific Realism. London: Routledge & Kegan Paul, 1963.

Spinoza, B. "Ethics." In The Collected Writings of Spinoza, Vol. 1. Translated by E. Curley. Princeton, NJ: Princeton University Press, 1985.

Strawson, P. F. Individuals, an Essay in Descriptive Metaphysics. London: Methuen, 1959.

Tichy, P. "An Approach to Intensional Analysis." Noûs 5 (1971): 273–297.

Tooley, M. Causation. Oxford: Oxford University Press, 1987.

Tooley, M., ed. Metaphysics. Vols. 1–5. New York: Garland, 1999.

Williams, D. C. "The Elements of Being." Review of Metaphysics 7 (1953): 3–18; 171–192.

Van Cleve, J. "Three Versions of the Bundle Theory." Philosophical Studies 47 (1985): 95–107.

Wittgenstein, L. Tractatus Logico-Philosophicus. London: Routledge & Kegan Paul, 1922.

Zalta, E. Abstract Objects: An Introduction to Axiomatic Metaphysics. Dordrecht, Holland: Reidel, 1983.

Graham Oddie (2005)

METAPHYSICS

From the Greek τὰ εξτὰ τὰφυσικκά (what comes after the physical) and the Latin metaphysica (after or beyond the physical), ontology, first philosophy, theology, wisdom, the philosophical science having as object being as being (τò ὄν[symbol omitted]ὁν, whence "ontology"), or the study of the meaning, structure, and principles of whatever is and inasmuch as it is or exists. In its material object, or the number of things it studies, metaphysics is all-inclusive, extending to everything and every aspect of whatever is or can exist, whether of a material, sensible, physical nature or of a higher, nonmaterial nature (from which extension to the most perfect and divine it is called "first philosophy" or "theology"). Nevertheless, metaphysics retains its distinctive point of vision, or formal object, inasmuch as it is concerned with things as beings, that is, according to the relation that any thing or aspect of things has to existence, rather than to one of the particular aspects treated in the other sciences. The unity of this point of view, centered on what is most fundamental to all reality, enables metaphysics to investigate the way in which the many are interrelated to the one in some form of real unity. Further, since things are reflected in knowledge, it enables metaphysics to order and evaluate the various types of speculative and practical knowledge (whence the term "wisdom").

The etymological derivation of metaphysics has been explained generally, though, it seems, erroneously, according to the theory of J. G. Buhle (1763 to 1821): from the fact that Andronicus of Rhodes (1st century b.c.) placed the treatises of Aristotle on this subject after the Physics for lack of any proper position in his scheme of the first complete edition of Aristotle's works. However, the name has been traced with probability by H. Reimer to Eudemus of Rhodes (3d century b.c.), the first editor of Aristotle's works, for whom it reflected not only that the subject matter in some sense transcends the physical aspect of things, but also the corresponding Aristotelian concern for the order of learning as proceeding from the more immediately sensible to the transcendent.

This article considers metaphysics in two parts. The first is concerned with its history, and the second with its elaboration as a science.

History of Metaphysics

Metaphysical thought arises from the wonder generated by the tension between the characteristics of things experienced as multiple, individual, and contingent on the one hand and those of truth as one, universal, and necessary on the other. The history of metaphysics is constituted by man's progressing toward a more penetrating mode of vision (formal subject) and the correlative intrinsic and extrinsic principles that enable him to understand both the many as constituting one order of reality and the one truth in its multiple realizations.

Primitive Origins. That man's mind is naturally metaphysical is indicated by the vision of reality as a whole and the concern for explanation manifested in the ancient myths (see myth and mythology). In Greece these were summarized in the Theogony of Hesiod, which stated the parts of the universe in the anthropomorphic form of the gods, unifying them in a genetic series and identifying in Eros an active principle for their interrelation. To attain a more precise view of this unity, it was necessary to supersede the anthropomorphic and symbolic form of the myths in order to attain a more explicit identification of their intellectual content and its source. This step was accomplished in concrete and personal terms by the Hebrews and in abstract terms by the Hindus and others in the East and by the Greeks in the West.

The Jews, from their earliest history to the Babylonian Exile in the 6th century b.c., under the tutelage of divine providence came to see that persons and things, however many, were one in their common dependence on God or, more exactly, in their dependence on a common God. "I am the first and I am the last; there is no God but me" [Is 44.6]. This unity in things was paralleled in the intentional order, where individuals by their fundamental response of mind and heart related themselves and their world to God. The repetition of this relation in concrete terms for single types of things ("who made the heavens in wisdom, … who spread out the earth upon the waters …"—Ps 135.5–6) manifests the need for a more abstract type of thought capable of identifying the proper extension and comprehension of the unifying relation to God.

The Oriental mind did carry metaphysical thought to the abstract and speculative level. hinduism in its scriptures, the upanishads, expressed a decisive appreciation of unity through the one impersonal substance, Brahman or Ātman, as the intimate reality of all things. However, fatally underestimating the world of experience as an illusion and source of suffering, it placed the road to wisdom in an ascetical and mystical science of withdrawal from activity and in a movement upward into natural contemplation of God as a prelude to reabsorption into Ātman. In the 6th century b.c., buddhism, having reduced all to empty phenomena in flux, held the supreme science to be one of deliverance from existence as such into the total indetermination called nirvĀna.

Greek Philosophy. The Greeks, in initiating their own speculative unification in the 6th century, b.c., possessed a firm appreciation of the reality of their world and a growing awareness of the value of intellectual clarity. Hence, their first steps were scientific in character, based on the evidence of the external senses and concluding in correlative terms that all was but particular states of water (Thales, c. 640 to 550) or other similar elements. Even here their concern opened beyond the merely physical to the metaphysical problem of overall unity, as is reflected in Anaximander's (c. 611 to 546) further reasoning to the "boundless" as beyond the diverse elements, unborn, all-encompassing, all-governing, and even divine [W. Jaeger, The Theology of the Early Greek Philosophers, tr. E. S. Robinson (Oxford 1947) 24–36]. pythagoras (c. 580 to 500), in holding all to be numbers, attained a second level of evidence corresponding to the internal senses. Finally, parmenides arrived at the third, uniquely intellectual, and metaphysical appreciation of the real in its own proper term, being. "Being is; for To Be is possible, and Nothingness is not possible," [figure 6, K. Freeman, Ancilla to the Pre-Socratic Philosophers (Cambridge, Massachusetts 1957) 43]. Since being could differ only by nonbeing, or nothing, Parmenides denied anything other than the one absolutely perfect and unchanging sphere. This gave being the meaning of identity or what can be thought (figure 3, ibid. ; figure 2, 42), contrasting with the position of heraclitus (540 to 475) that all was becoming. This contrast reflected the attainment by Greek philosophy of the properly metaphysical: the real as such—the explicit search for its internal and external principles and, in their terms, for the relation between the multiplicity manifested by experience and the unity appreciated by the mind. This search occupied the golden age of Greek philosophy.

plato (429 to 348) concluded from the fact of multiple beings to a principle of limitation or nonbeing as a "not-that-being" (Soph. 259A), and from the similarity among beings to something one or absolute in which the multiple participate as limited imitations. However, the combination of the Parmenidean meaning of being as intelligible identity with the Socratic method led to the transfer of reality from the multiple to that which the multiple imitate, the transcendent formal unities as Ideas to be contemplated and hierarchically ordered under the supreme Idea of the Good or the One (Republic 509). Man's highest calling and wisdom must then be to tend with all his powers, including the affective, to an ever clearer appreciation of the Ideas as the basis for guiding his actions (Symp. ).

aristotle (384 to 322), while retaining the goal of intellectual clarity and classically developing the division and structure of the sciences, initiated a more active understanding of form, based on a realist appreciation of the form of matter in changing things. This led him to forms separated from matter, which were not only objects of contemplation but themselves living, acting, knowing, and ultimately "the knowing on knowing" (νόησις νοήσεως νόησις Meta. 1074b 34). Related to this new level of reality was the distinct science of metaphysics, which in comparison to physics is both higher in dignity, because concerned with the unchanging, immaterial, and divine being, and broader in content, because concerned with being as being and hence all being (Meta. 1003a 20–1004a 1, 1025b 1–1026a 33). Aristotle, it seems, never perfectly conciliated the two understandings of metaphysics because his insight into being was not sufficient to allow for an understanding of the way in which the highest being could be the cause of being, as being in all beings. Despite the active understanding of form within the perspective of being as identity, form, and essence, the Parmenidean problem of the one and the many remained insoluble in these terms. This is seen from the limited attention given by the Greeks to the best manifestation of the simple affirmation of being, the person as a free and creative center in time and as capable of individual immortality. (see greek philosophy.)

Christianity. Christian thought presented the context for a penetrating insight into the act of being by underlining these very notions: in its distinguishing person from nature in the doctrine of the Trinity, and then in its heightening the appreciation of the created person's affirmation of self as gift in a response of love to the divine redemptive invitation to become sons, brothers, and heirs; and in its distinguishing creation from the Trinitarian processions, thus distinguishing form from the most formal effect of creation, the existence ("to be," or esse ) according to which a being is (the perfection of all perfections). The history of metaphysics in the Middle Ages consists in the major developments made possible by this more penetrating appreciation of being and evoked by the elaboration of the resultant theologies. These developments were made first on a more Platonic basis by St. augustine (354 to 430) and his school through St. bonaventure (1231 to 74), and then with an increasing addition of the Aristotelian systemization and realism by way of Arabian philosophy, culminating in the major syntheses of St. thomas aquinas (1224 to 1274), John duns scotus (c. 1274 to 1308), and others (see below).

Modern Era. Modern and contemporary metaphysics, finding the realistic metaphysics of being of the classical Christian philosophies of the Middle Ages already negated in the conceptualist philosophy of william of ockham (c. 1349) and his followers, proceeded to develop its metaphysics from the subject as manifested by the cogito of R. descartes (1596 to 1650). For the deleterious results, extending even to the negation of the possibility of metaphysics as a science, see metaphysics, validity of. Within this context, however, such classical rationalists as B. spinoza (1632 to 1677) and G. W. leibniz (1646 to 1727) contributed importantly to working out a logically deductive pattern of ideas; the schemata of the critical philosophy of I. Kant (1724 to 1804) and the dialectical sequences of G. W. F. hegel (1770 to 1831) further expressed reality's organic and developing character. Without realistic foundations, these philosophies inevitably progressed from positing that being is met in consciousness to idealism, holding that being is consciousness.

Contemporary metaphysics has sought to identify a place and a topic for metaphysical investigation that will be without presuppositions in order to allow the human mind most authentically to attain the real. In the transcendental phenomenology of E. husserl (1859 to 1938), philosophy is concerned with the knower and is directed toward grasping the world-constituting consciousness as such, rather than as one thing among many, because to grasp fully the possibilities of consciousness would be to grasp adequately being itself. For M. Heidegger (1889–1976), on the contrary, philosophy seeks the meaning of "to be" rather than of man, though the place of philosophical investigation is man in the world with others, the place in which "to be" has meaning for him. (see existential metaphysics and existentialism for a discussion of the existential emphasis in recent Thomistic thought and in contemporary forms of existentialism.) Together, the rationalistic and existentialistic developments of modern times have achieved a more reflective appreciation of man's grasp of being and of its personal dimension.

The Science of Metaphysics

The history of metaphysics manifests a universal striving of the human mind to clarify its appreciation of reality as a unified whole. To do this effectively, the mind must pass beyond the simple constatation of a unified reality to the discovery of its causes by means of science (scientia), the discursive process leading to the perfect knowledge of its subject by discovering its causes and attributes (Thomas Aquinas, In meta., proem.; In 1 anal. post. 2.3). As the attributes are related to the subject through the middle term, which is the real definition of the quiddity of the subject (In 2 anal. post. 1.9), the subject is not only the term concerning which knowledge is sought but also the source and norm of the scientific knowledge that concerns it. It was the diversity of meanings historically attributed to being (identity, substance, "to be") as the subject that lay at the root of the various forms of metaphysics noted above; and if a metaphysics is to be a study of reality itself as act or as a relation to existence, it can be so only if this be the nature of its proper subject.

Initiation of the Science. As there is nothing in the intellect that was not first in the senses, the realistic character of scientific knowledge immediately implies two levels of abstraction, of subjects, and hence of speculative sciences: physics abstracting from individual matter and proceeding on the evidence from the external senses to study things as expressed by qualities, and mathematics abstracting from common sensible matter and proceeding on the evidence of the internal senses to study things as quantified (see sciences, classifications of). Being, as a third level of formal subject prescinding from all matter, has been proposed on various bases: (1) a simple dissociation based on the mind's recognition that being and material are not equivalent, even though no special evidence for this be given; (2) a gradual process of removing the various specifications from being till there remains only a univocal "not nothing" of minimal significance; and (3) a separation of being as esse based outside the natural order on the common Judeo-Christian revelation of God as "I am who am" (Ex 3.14). Whatever be said about the distinctive value or problems of these approaches, the perfection of metaphysics as a distinct human science seems to require: first, that its subject, whose real definition is the middle term in the discursive process of metaphysics, be drawn from material things, the quiddity of which is the proper object of the human intellect (In Boeth. de Trin. 5.4); second, that the separation of a distinct meaning for being from material being be validated by the witness of actually existing nonmaterial beings (In 4 Meta. 5.593).

This fact of nonmaterial reality has been reflected constantly by man's commonsense appreciation of a power that transcends man; of the human person as a unique subject of justice, love, and freedom; and of his many social and artistic expressions. Although all these manifest a level of nonmaterial reality untouched by the sciences of the first two degrees of abstraction, the initiation of the science of metaphysics itself is better supported by the full strength of the scientific knowledge. Phenomenological investigations have usefully reflected on man as the crossroads where the flesh assumes the spirit and the spirit becomes incarnate; but the attainment of being as act is most amply founded on natural beings experienced as existing on as broad a base as can be provided by the following combination of all the nonmetaphysical sciences.

Aristotle's classical statement of the structure of the science of physics leads to the nonmaterial after identifying form and matter as changing being's intrinsic principles. However, this composition is shown in the Physics (books 7 and 8) to manifest a dependence for its ultimate explanation on something nonmaterial. Though, in physics, this can be described only in such negative and relative terms as "not material," "not changing," "not spatial," and "not temporal," physics does establish the existence of the nonmaterial as presupposed for whatever reality is had by physical substances and their accidents. In Aristotle's De anima and in his other psychological writings, the nonmaterial character of man's acts of intellection and volition are seen to manifest the nonmaterial character of his substantial form, or soul (see soul, human; spirit). Here, the extensive recent insights concerning human consciousness and freedom and the related significance of all dimensions of man and the universe give further indication of the reality and significance of the nonmaterial. Again, exemplary causality,, in relation to the speculative science of mathematics and its principles, allows the reality of the mathematical to manifest a higher and nonmaterial reality. Finally, in the practical order, the investigation of the end, or goal, required to open the full scope of man's free activity is seen as the contemplation of something transcending the material. Hence, as the human mind establishes the scientific processes by which it extends its knowledge with a controlled certainty and necessity to the various dimensions of reality, it becomes increasingly aware of the reality of the nonmaterial.

By this fact of immaterial reality, the mind is enabled to make the negative judgment of separation that the real is not necessarily material. It can also conclude that what makes the real to be real, the real precisely as real, is not material—though, of course, many real beings are really material (In Boeth. de Trin. 5.3, 4, and ad 5). By this negative judgment the mind removes a restriction to its understanding of things. Hence, whereas previously, having attained all things through the senses, it spoke of reality precisely as sensible, it is now able to speak of these distinctively according to that by which they are real. The mind also knows that real is not simply a more general term for what had previously been stated more specifically. Because it knows that there are some things that exist but are not material, it knows that to speak of things precisely as real is to express them in a way that is more fundamental and penetrating than are any of their prior modes of attainment.

From the above, it can be seen that the common notion of being (being as being, being in general), which is the subject of the science of metaphysics, is expressed by "what is," for being affirms in act "what" is and of whatever kind, and does so by the "to be," which, as the actuality of all determinations of kind or nature, is the most formal element in being. Together the "what," or essence, and the "is," or "to be," or existence, express the notion of being (see being; essence and existence; potency and act).

From the foundation and mode of separation of being, it is also clear that the resulting notion is not a univocal least common denominator, whose differences have been progressively removed; rather, it actually includes the reality of all such differences precisely as real, even if only implicitly. At the same time, the notion of being is not equivocal (nominalism), lacking in any common significance in its application to the many different things. On the contrary, the notion of being is analogical; that is, it includes within itself the differences by which beings are really distinct one from another—it is different simply in its application to distinct things while at the same time it has a certain similarity in its significance when applied to each of them (see analogy).

Elaboration of the Science. After it is seen that the subject of metaphysics is being, and that its mode is analogical, the first and necessary phase of the science of metaphysics is to identify the properties of its subject, thus unfolding its meaning. These properties could not be really distinct from being in its transcendence; rather, they express explicitly what already is implicit, but actual, in being itself (De ver. 1.1). They include unity, truth, goodness, and beauty. By unity being is identified as indivisible within itself, that is, as not shared with what it is not or with nonbeing and, by implication, as divided from all other beings (see unity). Being in its identity is able to be present in the intellect, and hence to be true (see all truth ). Being, as an intelligible identity, is also able to be related to the will, and hence to be good (see good). All of these are drawn together in the property of beauty, which is being inasmuch as it pleases when seen (see beauty). Parallel to these transcendental properties, and expressive of them in the form of judgments of being as possessing these properties, are the first principles of being (see first principles). To being as one, there correspond the principle of contradiction: being is not nonbeing; and the principle of identity: being is being, or being is itself. To being as true, there corresponds the principle of sufficient reason. Finally, to being as the transcendent good, there corresponds the principle of finality. Once the subject of metaphysics has been attained, these properties and principles can be discovered by an analytic process reflecting on the significance of what it means to be. In fact, Parmenides made notable accomplishments in this phase of metaphysics, even though he maintained that there could be but one being.

In order to go further into the science of metaphysics and to discover the intrinsic principles of its subject and the external relationship between beings, it is necessary to introduce the more synthetic phase of metaphysical method, wherein the mind returns to the experiential order and its evidence for a plurality of beings. This evidence, understood in terms of being as being and its property of unity, poses the problem of the one and many for the first time in direct metaphysical terms. This, indeed, includes two problems: first, how there can be more than one being or how being can be limited and, second, how these many beings, while differing one from another, can still be similar as beings.

The limitation of being opens to the mind the reality of a limiting principle that is not existence, but is inside the being, forming a unity with the existence to which it is related as potency to act. As allowing the mind to attain an insight into the internal structure of multiple and, hence, finite being, this reflection is of the greatest moment for the development of the science of metaphysics; in it, Aquinas achieved his synthesis of Christian platonism and aristotelianism. This discovery concerning internal structure is paralleled by another concerning extrinsic relations; this springs from the second problem, concerning the way in which the many can be similar as beings, and yet distinct from one another. This, together with the problem of the actuation of the potency, opens the path for the mind to Absolute Being, the cause of the subject of metaphysics. The essence of this Being is Its existence, a Subsistent Existence and pure act in which all multiple beings participate precisely as being, or according to their relation to existence. Thus is established a unity between all beings such that the absolute unity identified by Parmenides as characteristic of being is not destroyed but rather is opened out to a subordinate realm of multiple and participating beings (see participation).

In similar cycles the problem of the one and the many considered synthetically yields evidence of new unities. These are either unities of a specific kind among the multiple beings that lead to knowledge of the actpotency structure of form and matter within essence and further to the Divine Mind for the ultimate explanation of specific unities; or they are unities of many accidents as acts of the one substance, laying the foundation for a further union between beings by causality. Hence, the science of metaphysics gradually unfolds by a process of analysis and synthesis wherein it elaborates the internal principles and the external causes of its subject, being as being, and comes to understand all things in the light of these.

Characteristics. Such a metaphysics is supreme in universality, intellectuality, and certitude. (In Meta., proem.). The distinctive universality is had, first, according to comprehension, for the formal subject of the science is the most fundamental value of all, the relation to existence; second, according to extension, for, studying things as beings, the science is transcendent in its concerns, extending to every being and aspect of being; and finally, according to dignity, inasmuch as it carries the mind even to the divine in its search for the cause of its subject.

A second characteristic of metaphysics is its supreme intellectuality. Intellectuality is a mode according to which all is comprehended in one simple act and idea that attains the full truth of manifold beings and their principles. The human mind, proceeding abstractively, approaches this ideal imperfectly, but truly, to the degree that it is able to unify its knowledge of all things in one formal subject, through which it attains a uniquely simple, immediate, and comprehensive intellectual knowledge (In Boeth. de Trin. 6.1.3 ad 1). This special intellectuality is had by metaphysics inasmuch as its formal subject is being, the common object of the intellect and the source from which its principles are derived immediately and its conclusions most directly. Hence, if difficult of attainment, metaphysics has a most profound proportion to the human intellect, with its actual and possible openness to being.

The third characteristic of metaphysics as a science follows from the above. This is its special objective certitude, which derives from its subject and from its reasoning processes, as founded and verified in the first and most evident of all principles, the principle of contradiction.

Fourth, as the science that is most perfectly universal, intellectual, and certain, metaphysics takes on the character of natural wisdom. For if the wise man, as Aristotle describes him, must have universal and difficult knowledge, greater than ordinary certitude, and a capacity to identify causes, to seek knowledge for its own sake, and to be able to rule others, then metaphysics fulfills this necessity. It is the most universal science, extending even to what most transcends the human mind; yet it has the greatest certitude and commitment because concerned with being itself; and finally, because it knows the principles of all being, it is able to rule and direct the sciences that are concerned with particular types of beings. Metaphysics, therefore, stands at the culmination of man's knowledge; it derives from a negative judgment based on evidence from all the sciences, and, as a potential whole, it is present in the exercise of all other intellectual virtues, wherein it is but partially expressed. Since it uses other sciences to enlarge its knowledge, its ordering function in their regard is part of the work of wisdom itself.

Thus metaphysics takes on a supreme human value."The ultimate perfection which the soul can attain, therefore, is, according to the philosophers, to have delineated in it the entire order and causes of the universe. This they hold to be the ultimate end of man. We, however, hold that it consists in the vision of God" (De ver. 2.2).

See Also: wisdom; theology, natural;christian philosophy; philosophy.

Bibliography: c. fabro, La nozione metafisica di partecipazione secondo S. Tommaso d'Aquino (2d ed. Turin 1950); Participation et causalité selon S. Thomas d'Aquin (Louvain 1961). j. definance, Être et agir dans la philosophie de saint Thomas (Paris 1945). É. h. gilson, Being and Some Philosophers (2d ed. Toronto 1952). t. c. o'brien, Metaphysics and the Existence of God (Washington 1960). l. j. eslick, "What Is the Starting Point of Metaphysics?" The Modern Schoolman 34 (1957) 247–63. l. b. geiger, "Abstraction et séparation d'après S. Thomas," Revue des sciences philosophiques et théologiques 31 (1947) 3–40. a. mansion, "Philosophie première, philosophie seconde et métaphysique chez Aristotle," Revue philosophique de Louvain 56 (1958) 165–221. r.w. schmidt, "L'emploi de la séparation en métaphysique," ibid., 58 (1960) 373–93. j. d. robert, "La métaphysique, science distincte de toute autre discipline philosophique, selon saint Thomas d'Aquin," Divus Thomas 3d series 50 (1947) 206–22. v. e. smith, "The Prime Mover: Physical and Metaphysical Considerations," American Catholic Philosophical Association. Proceedings of the Annual Meeting 28 (1954) 78–94. h. heiner, "Die Entstetehung und ursprungliche Bedeutung des Namens Metaphysik," Zeitschrift für philosophische Forschung 8 (1954) 210–37. t. andoŌ, Metaphysics: A Critical Survey of Its Meaning (The Hague 1963). g. gusdorf, Mythe et métaphysique (Paris 1953).

[g. f. mclean]

METAPHYSICS

METAPHYSICS is generally understood as a philosophical inquiry into the fundamental nature of reality. The word metaphysics derives from the Greek meta ta phusica ("after the things of nature"), a classificatory rubric used by commentators on and editors of Aristotle's corpus to refer to an untitled group of texts concerned with "first philosophy." Western medieval and modern philosophers often have construed metaphysics as the most basic and most comprehensive of philosophical inquiries, one that is primarily focused on the ontological status of objects, the existence of entities that transcend nature, and the generic features exhibited in experience. African and Eastern philosophers usually have conceived of metaphysics (in the sense implied by the word's etymology) as more closely interwoven with the axiological (or value-laden) character of the cosmos and the moral quality of human community.

A distinctive feature of Western metaphysics is the attempt to understand the universe by means of a logical investigation of concepts rather than an empirical inquiry based on sensory evidence. Such metaphysical sentiments rest upon a relative distrust of the variable, visible, and sensible world and involve a quest for the invariable, invisible, and intelligible world. They also assume a basic unity of thought and being, of logic and the world. Rationally coherent and logically consistent systems of thought are believed to reveal the way the world really is.

The origins of Western metaphysics go back to Parmenides of Elea (c. 515–475 bce). In the poem usually titled On Nature, Parmenides provides the first exemplary philosophical argument of Western metaphysics. In the form of a journey to the heavens to receive wisdom from "the goddess," Parmenides attacks the reality of the physical world, condemns difference as illusory, and proposes that fundamental reality is invariable, invisible, and intelligible, as well as single, indivisible, and homogeneous. This metaphysical viewpoint rests upon the deployment of the basic binary opposition of reality and appearance, in which the realm of the former is qualitatively different from and superior to the realm of the latter.

Parmenides' metaphysical conception of being, grounded in his logical reasoning and monistic conclusions, has been a major influence in Western metaphysics. This Parmenidean legacy can be seen in Plotinus's One, Spinoza's God, and Hegel's Absolute. The most immediate influence of Parmenides is found in Plato's Phaedo, in which, despite subtle gradations, the reality/appearance distinction is appropriated to undergird the existence of a separate order of Forms accessible only to the mind and more real than the senses. In his heroic efforts to refute the skepticism of the Sophists, Plato (427–347 bce) extends the ontological binary opposition of reality/appearance to epistemology, morality, and politics, thus including distinctions such as knowledge/opinion, nature/convention, and philosopher/sophist. In this way, Plato's metaphysics, like that of some African and Eastern thinkers, is inseparable from ethics and political philosophy.

The religious significance of Plato's metaphysics is his doctrine of recollection, which defends the immortality of the soul. In Meno, Plato portrays Socrates interrogating a slave boy, an interrogation that results in the boy arriving at a geometric truth. Socrates then argues that since this truth was not told to the boy but rather elicited from him, the truth must reside in the boy at birth and in a previous existence: his questions merely prompted the boy to remember what he had forgotten from an earlier life. Similar arguments, related to the existence of a separate order of Forms, are found in the Phaedo, while a more speculative account of the transmigration of souls, life after death, and the soul fleeing the bondage of the body is put forward in the tenth book of the Republic.

Aristotle (384–322 bce) set forth the first Western metaphysical system, including a new vocabulary, an articulation of the central issues, and a thorough treatment of these issues. He conceives of metaphysics as a "first philosophy" that investigates the fundamental principles presupposed by the other sciences. Aristotle's metaphysics can be viewed as a profound and persistent polemic against the notions of indeterminacy and infinity. Its aim is to establish a fixed beginning point, the limits of inquiry, the determinateness of concrete individual objects, and the termination of epistemic chains of justification. Aristotelian notions of causality (material, formal, efficient, and final), substance, being, essence, form, and actuality set the terms for Western metaphysical discourse through the twentieth century. The legacy of Aristotle's metaphysics in religious thought is found most clearly in the Christian systematic theology of Thomas Aquinas and the neo-Thomist tradition of the Catholic church exemplified in thinkers such as Étienne Gilson (1884–1978) and Jacques Maritain (1882–1973).

The last great metaphysical system of classical antiquity was the Neoplatonism best represented by the Hellenized Egyptian philosopher Plotinus (205–270 ce), his pupil Porphyry (232–306?), the Syrian school of Iamblichus (250–330?), the Athenian school of Proclus (c. 410–485), and the Latin Christian school of Boethius (480–524). This system (and its various versions) is rooted in Plato's devaluation of the sensible world and elevation of the intelligible world. Yet, as in certain themes in Plato's second and seventh letters, Neoplatonism promotes a kind of mysticism and asceticism that deeply influenced the Christian theology of the African thinker Augustine (354–430). This mysticism is based on an intuition of the unity and wholeness of being, the One, which differentiates itself downward into lesser degrees in spirits, souls, and, lastly, physical objects. This process of emanation from undifferentiated unity to modes of differentiated disunity results in a return (or epistrophe) to unity and wholeness.

The Syrian philosopher Porphyry not only made Plotinus's lectures available but also wrote a short introduction to Aristotle's Categories, titled Isagoge, that directed attention to the relation between the essential and accidental attributes of things and the status of universals. This influential text, translated into Latin by Boethius, provided the framework and language for metaphysical reflection in the early Middle Ages by Christian theologians such as John Scottus Eriugena (fl. 847–877), Anselm (c. 1033–1109), and Bonaventure (c. 1221–1274).

The thirteenth-century translations of Aristotle and his Arabian commentators into Greek and Latin by Robert Grosseteste and William of Moerbeke facilitated the crowning achievement of Western metaphysics in the late Middle Ages: the magisterial system of Thomas Aquinas (c. 1224–1274) and the critical nominalism of William of Ockham (c. 1280/1285–1349?). Thomas creatively appropriated Aristotelian metaphysics into a Christian philosophy, whereas William paved the road for the new "modern way" (via moderna ) by separating metaphysics from Christian faith and thereby emphasizing religious faith and church tradition. William influenced major figures of the Reformation.

The modern conception of metaphysics in the West begins with René Descartes (1596–1650), who tried to apply the rigor and standards of mathematics and geometry to metaphysical claims. Descartes's quest for indubitability within the immediate awareness of a thinking self and his call for clarity and distinctness in truth-claims reflect an ingenious and influential philosophical response to the rise of modern science, especially the wedding of quantitative models with physics and chemistry. Barukh Spinoza (1632–1677) and Gottfried Wilhelm Leibniz (1646–1716) followed the Cartesian project of scientific rigor and philosophical boldness by setting forth deductive metaphysical systems. Spinoza's mechanical and deterministic view of the universe, in which the only two known attributes of substance are thought and extension, yielded a pantheistic conception of God as identical with nature. This conception would inspire later forms of German idealism. Leibniz's rationalist commitments to a priori reasoning, the analysis of concepts according to logical necessity and rational intelligibility, produced refined versions of ontological arguments for the existence of God that sharpened modal logical tools for subsequent efforts by Christian theists.

The crisis of modern Western metaphysics begins with the major empiricists: John Locke (1632–1704), George Berkeley (1685–1753), and, especially, David Hume (1711–1776). All three assumed the Cartesian starting point for philosophical reflection as within the arena of immediate awareness of a thinking self. But in contrast to Descartes, Locke argues that sense impressions are the primary data for knowledge of the world, self, and God. This restriction requires that we cannot have "clear and distinct ideas" of substance and essence, only empirical access to their properties and powers. Therefore, the most privileged notions in traditional Western metaphysics, such as substance and essence, were rendered problematic. Berkeley further questioned the distinction between ideas of objects and properties of objects that cause ideas, thereby radically calling into question material substance. Hume changed the course of Western metaphysics by dissolving philosophical conceptions of the self, subject, and mind into mere bundles of sensations and perceptions. By replacing philosophical notions of necessity and causality with psychological accounts of imagination and sociological notions of habit and custom, Hume defended an inescapable skepticism regarding the possibility of metaphysics. This position presented religious thinkers with the options of a rational agnosticism or a nonrational religious faith.

The significance of Immanuel Kant (1724–1804) lies in his rescue of Western metaphysics by specifying the limits of human knowledge. This rescue took the form of rejecting the dogmatism of Cartesian metaphysical projects and circumscribing the skepticism of Hume's empiricism. The result was a critical idealist metaphysics that preserved the objectivity of knowledge-claims yet prevented human access to ultimate reality. The aim of Kant's metaphysics was to disclose the universal conceptual scheme that people employ in theoretically ordering the world and practically acting within it. For Kant, religious faith became a mere appendage to ethics, a practical postulate for moral behavior.

The last great metaphysical system in the modern West—a response, in part, to Kant—was that of Georg Wilhelm Friedrich Hegel (1770–1831). Like Plato, Aristotle, and the Neoplatonists, Hegel attempted to penetrate to the fundamental nature of reality by means of rational deliberation. Yet he conceived of this reality as a historical and dialectical process intelligible only to the discerning and retrospective philosopher. Hegel's metaphysics emphasized the radical dependence of God upon the world and promoted a divine immanent presence in human history.

Western metaphysics has been under severe attack since Hegel. Apart from the ambitious project of Alfred North Whitehead (1861–1947), the vitalistic program of Henri Bergson (1859–1941), the versions of logical atomism of Bertrand Russell (1872–1970) and the early Ludwig Wittgenstein (1889–1951), and Paul Ricoeur's (b. 1913) recent metaphysics of narrativity, post-Hegelian philosophy has been strongly antimetaphysical. The Christian existentialism of Søren Kierkegaard (1813–1855) and the transcendental phenomenology of Edmund Husserl (1859–1938) inspired the ontological hermeneutics of Martin Heidegger (1889–1976), which claims to have "destroyed" the Western metaphysical tradition. The logical positivism of the Vienna Circle (Otto Neurath, Moritz Schlick, Rudolf Carnap, and others) and ordinary-language philosophy served as stepping-stones for the later Ludwig Wittgenstein's linguistic conventionalism, which claims to have "dodged" the bewitching traps of Western metaphysics. The perspectivism of Friedrich Nietzsche (1844–1900) and the structuralist vocabulary of Ferdinand de Saussure (1857–1913) provided resources for the present-day poststructuralist skepticism of Jacques Derrida (1930–2004), which claims to have "deconstructed" the Western metaphysical tradition. Lastly, the pragmatism of William James (1842–1910) and John Dewey (1859–1952) and the epistemological holism of W. V. Quine (1908–2000) and Nelson Goodman (1906–1998) are employed by Richard Rorty (b. 1931) in his contemporary attempt to "demythologize" the Western metaphysical tradition. Whether the influential attacks of Heidegger, Wittgenstein, Derrida, and Rorty on Western metaphysics are skeptical moments in the history of Western philosophy (like those of Pyrrho and Montaigne in times past) or proleptic precursors of a new stage remains an open question. The religious significance and implications of these attacks—within and outside the West—remain relatively unexplored.

Bibliography

Ayer, A. J. Philosophy in the Twentieth Century. New York, 1982. A noteworthy and well-written sequel to Bertrand Russell's A History of Western Philosophy (1945) by a major figure active on the contemporary scene since the 1930s.

Hancock, Roger. "Metaphysics, History of." In The Encyclopedia of Philosophy, edited by Paul Edwards, vol. 5. New York, 1967. The best short and concise article-length treatment of major historical developments in Western metaphysics. An extensive bibliography on central figures and periods is included.

Passmore, John. A Hundred Years of Philosophy. 2d ed. Middlesex, U.K., 1970. The most comprehensive and detailed history of academic Western philosophy dealing with post-Hegelian developments. Reliable reportage and exposition, but lacks an overarching interpretive framework.

Rorty, Richard. Philosophy and the Mirror of Nature. Princeton, 1979. A highly provocative, imaginative, and learned interpretation of Western philosophy that puts forward devastating critiques of metaphysics.

Russell, Bertrand. A History of Western Philosophy. New York, 1945. The most informative, stimulating, and engaging history of Western philosophy available in one volume in English, by one of the most brilliant thinkers of the twentieth century.

New Sources

Levinas, Emmanuel. Otherwise than Being: Or Beyond Essence. Translated by Alphonso Lingis. Pittsburgh, Pa., 1998.

Lewis, David. On the Plurality of Worlds. Oxford, U.K., 2000.

McCumber, John. Metaphysics and Oppression: Heidegger's Challenge to Western Philosophy. Bloomington, Ind., 1999.

Miklowitz, Paul. Metaphysics to Metafictions: Hegel, Nietzsche, and the End of Philosophy. Albany, N.Y., 1998.

Silverman, Allan Jay. The Dialectic of Essence: A Study of Plato's Metaphysics. Princeton, 2002.

Cornel West (1987)

Revised Bibliography

METAPHYSICS

Metaphysics is concerned with human thinking about the nature of reality in the widest and most general sense. A general worldview of this kind will be influenced by what physics has to say about the character of the universe, but it will not be determined by this alone. Other forms of knowledge must also be brought into play. Physics constrains metaphysics, but it does not entail it, as the foundations of a house constrain what can be erected upon them, but they do not fix the form of the edifice. The proper relationship between physics and metaphysics is that of consonance and not one of deductive necessity.

In this kind of intellectual exchange, particle physics has been one of the most metaphysically influential branches of physics because of its ability to discuss the basic constituents out of which the variety of the physical world appears to be constructed. Its influence on general human thinking has been varied and contentious, however, just because of the ambiguity inherent in attempting to move from the particularities of physics to the generalities of metaphysics.

History

The pre-Socratic philosophers, such as Thales and Anaximander, considered that the variety of the world resulted from different states of a single kind of basic stuff. Thales assigned water to this fundamental role, while Anaximander favored air. The intuition that simplicity underlay apparent complexity was brilliant (one could think of the pre-Socratics as proto-particle physicists), but these early thinkers were unable to develop their ideas in any plausible detail. It was Leucippus and Democritus in the fifth century b.c.e. who took the further important step of proposing the existence of irreducible atoms (the Greek word means "uncut"), whose motions in the void constituted the nature of the world. The idea was developed more than a century later by Epicurus to form the basis of his atheistic philosophy. This way of thinking was fluently and fervently expounded by the Latin poet Lucretius in his influential poem De Rerum Natura (On the nature of things, 58 b.c.e.).

Atomism became of renewed interest in the seventeenth century with the rise of modern science. On this occasion, however, its principal proponents, such as Robert Boyle and Isaac Newton, were theists. It was only later, principally in eighteenth-century France, that atomism again began to be associated with atheism. Atomism in a recognizably modern form dates from the beginning of the nineteenth century, starting with John Dalton's development of his atomic theory of chemistry. This enabled Dalton to bring impressive order into a complex collection of data relating to chemical interactions. He himself was a Quaker.

Modern Developments

For the contemporary particle physicist, atoms are very large-scale systems, and they are certainly not uncuttable. Current candidates for basic constituents are at least as small as quarks and gluons and perhaps as infinitesimal as superstrings. Two aspects of the chain of discovery linking Dalton to the Standard Model of contemporary particle physics have particularly impressed themselves on the thinking of a wider intellectual public. One is simply the success of the program in accounting for many of the properties of the physical world in terms of the behavior of a small set of basic constituents. The other striking feature has been that at each level in the exploration of the structure of matter the resulting theories have been characterized by elegant economy and simplicity. Just as Dalton's atomic theory succeeded in bringing order into a bewildering welter of chemical facts, so contemporary particle physics uses the search for underlying simplicity as a successful guide to the discovery of yet more basic theories.

Such success raises the question of whether these elemental entities are not entitled to the metaphysically more profound epithet "fundamental." Are they, in fact, the stuff of reality, so that a particle physics perspective is the right way to approach metaphysics, with the other levels of human experience of the world simply being the complex corollaries of the aggregation of elementary entities? To ask the question raises the issue of reductionism (thinking in terms of constituents) versus holism (thinking in terms of totalities). If the former stance were the totally correct one, particle physics would not only influence human thought—it would be the proper basis for all fundamental human thinking. But this would be a metaphysical, rather than a scientific, conclusion.

Reductionism

Reductionism is the way of thinking that concentrates on an understanding founded in terms of the properties of constituents, rather than in terms of entities considered as a whole. The atheistic thinking of Epicurus was strongly reductionist—atoms and the void constituted the actual nature of reality. The examples of Boyle and Newton show, however, that atomistic thinking need not lead either to atheism or to the view that atomism is the all-sufficient account of reality. In the introduction the ambiguity inherent in the relation between physics and metaphysics is noted. The issues at stake for human thought can be clarified by recognizing that there are a variety of distinct forms of reductionist thinking.

First, there is a strategy of enquiry that can be called methodological reductionism. The complex character of totalities means that if they are decomposed into their component parts, these constituents will often be much easier to understand. Much can be learned by this technique of intellectual "divide and rule," and particle physics is the ultimate reductionist subject in this sense. Its successes indicate that this is indeed a very fruitful procedure to follow. It by no means follows, however, that one can learn all that is knowable and worth knowing by following this reductive tactic alone. The success of regarding sub-atomic matter as composed of quarks and gluons does not at all imply that this is all that needs to be said about physical reality.

A second form of reductionism corresponds to what may be called ontological reductionism. This asserts that when the decomposition of systems into their smallest parts is actually carried out, the entities that will be found among the fragments are indeed those that particle physics describes. Adopting this point of view implies, for example, that there is no "extra ingredient" necessary for living entities of the kind that vitalism supposed to be required. This form of reductionism is very widely accepted, and it is reinforced by the successes of molecular biology in giving an account of the processes taking place within living cells. However, it does not follow from this acceptance that higher-level entities are "nothing but" collections of quarks and gluons. That this caveat is necessary can be seen by considering the truth or falsehood of a third form of reductionism.

This is conceptual reductionism. This would claim that the concepts used in physics are all reducible to being expressed in terms of elementary particle physics; that all of chemistry is reducible to physics; and so on. Many thinkers reject this view. Its implausibility seems clear enough within physics itself. Subjects such as condensed matter physics and fluid mechanics make use of concepts that cannot be expressed just in terms of elementary entities. Single atoms have neither temperature nor viscosity. Although there has been a tendency among some particle physicists to call the currently unknown Grand Unified Theory a "Theory of Everything," that claim is overblown. More persuasive is the remark made by the condensed matter theorist, Philip Anderson, that "more is different." New properties emerge at higher levels of complexity, and they have to be treated on their own terms.

Some emergent properties are intricate but, in principle, unproblematic. An example is wetness. H₂O molecules individually do not exhibit this property, but it is scarcely surprising that when large numbers of them are brought together, the resulting redistribution of energy due to intermolecular interactions results in the collective effect that we call surface tension. This insight is an example of causal reductionism. The phenomenon of wetness is capable of being understood as due to effects operating at the atomic, and ultimately at the particle, level of causation. It is not at all clear, however, that all emergences are capable of being satisfactorily understood in this causally reductive way. There are emergences that appear to differ qualitatively from the properties of the substrate that sustains them. The most striking example is consciousness. Many see a yawning gap between neuroscience's talk of neural interactions, however interesting and sophisticated such talk may be, and the simplest mental experience, such as that of seeing pink. The execution of a willed intention obviously involves lower-order processes, such as muscle contractions, but it is not at all obvious that there is not also a new kind of mental causality that has also been brought into play. The issue here is essentially metaphysical, and it certainly cannot be settled by particle physics.

The most significant issue concerning the relationship of particle physics to human thought concerns the status of the entities that it describes. Are they simply an interesting and significant level in the structure of reality, or are they to be considered as "more fundamental" than other entities, such as cells or human beings? The question is a metaphysical one. Strong opinions can be expressed on either side of the issue, but it is not one that particle physics itself can settle.

See also:Benefits of Particle Physics to Society; Culture and Particle Physics; Influence on Science; Philosophy and Particle Physics; Universe

Bibliography

Barrow, J. D. Theories of Everything: The Quest for Ultimate Explanation (Oxford University Press, Oxford, UK, 1991).

Cushing, J. T. Philosophical Concepts in Physics: The Historical Relation between Philosophy and Scientific Theories (Cambridge University Press, Cambridge, UK, 1998).

Penrose, R. The Large, the Small and the Human Mind (Cam-bridge University Press, Cambridge, UK, 1997).

Polkinghorne, J. C. Beyond Science: The Wider Human Context (Cambridge University Press, Cambridge, UK, 1996).

Weinberg, S. Dreams of a Final Theory: The Search for the Fundamental Laws of Nature (Pantheon Books, New York, 1992).

John Polkinghorne

Metaphysics

The term metaphysics refers to the study of things that are removed from sense perception. Modern metaphysics studies the kind of things that exist and the way they exist.

In the dialogue of science and religion, metaphysics, science, and religion do not necessarily refer to separate endeavors that need relating. Religious faith, for example, can be pervasive so that nature is seen as divine creation and science as a form of worship. Neither do the terms refer to universal bodies of knowledge and belief independent of context. Metaphysics has affected the dialogue between science and religion. These effects have depended on the content of metaphysics and on whether it functioned as science or religion. Moreover, metaphysics and religion have shaped epistemology. Metaphysics has served as presupposition, sanction, motive, criterion for theory choice, criterion for the choice of kinds of explanation (regulative principle), and as part of explanations (constitutive principle). The focus in the dialogue between religion and science is on how God interacts with the world, and on the relation between knowledge of God (religious knowledge and the systematic reflection on it in theology) and knowledge of nature (views of nature, as well as the systematic development of empirical knowledge).

Ancient Greek metaphysics shaped the understanding of God's action in the world in each of the three Abrahamic religions. (Eastern Orthodoxy is an exception in this respect while Judaism can be said to have been only insignificantly influenced.) In Christianity and Islam, the possibility of dialogue between religion and science depended, among other considerations, on how the relationship between theory and observation was envisioned. For ancient Greek philosophers, reliable knowledge was knowledge of the ultimate. Different types of metaphysics had preferred ways of knowing ultimate reality. The Platonic ideas were best known by reason. For Democritus, the random movement of atoms was ultimate reality; their material combinations were best apprehended by sensation. Sensation was also the only source of knowledge of nature for the nominalists, who denied the existence of universal ideas. This reinforced the distinction between observation and reason in eleventh- and twelfth-century scholasticism. To protect divine intervention from naturalistic explanation, theologians distinguished between God's ordained power operating in regular natural phenomena and his absolute power manifested in miracles. In addition, reasoning in theology was limited to avoid conflict with divinely revealed knowledge. Thus the possibility and nature of dialogue between science and religion came to depend on how the relationship between nature and supernature was envisioned.

Metaphysics affected the dialogue between natural philosophy and religion via the content of both. While in Greek metaphysics the order of nature was autonomous and necessary, in the Abrahamic religions it depended totally upon the creator. These traditions were combined by medieval Christian theologians. They acknowledged both a relative autonomy of nature (God's ordinary power) and a divine sovereignty (God's absolute power). Yet theological responses also included the naturalism of William of Conches (c. 1080–c.1150). This set the stage for future discussions. One question was whether purpose in organisms reveals God's natural or supernatural action. Thomas Aquinas (c. 1225–1274) interpreted Aristotle's natural final cause as divine providence, thereby creating a link between natural philosophy and religion. When natural philosophers took purpose as a natural cause, theologians saw the power of God diminished. In response, different forms of voluntarism developed in both Muslim and Christian theology in which creatures were denied causal power because it detracted from God's power. When theologians insisted on God's purposive action in organisms, natural philosophers indicated that God could act through natural law. Responses to these questions regulated the content of both theology and natural philosophy. If animals generate their own purposes, Aquinas considered, inanimate things could prove God's existence more convincingly. Therefore, Aquinas excluded animals from his teleological proof for the existence of God. William Harvey (1578–1657) believed that everything has a God-given purpose. He reasoned that venous valves were created pointing in the same direction in order to prevent reverse flow and to assure the continuous circulation of blood.

In Western Christianity, the idea of absolute divine power did not discourage the exploration of nature's regularities because it was balanced by the idea of ordained power. No such balancing act occurred in the Ashirite school of Muslim theology even though it distinguished between Allah's absolute power and the derived power of humans. This distinction was not applied to natural phenomena. The Ashirites believed Allah creates a cause especially for the occasion of a phenomenon according to a regular pattern of cause and effect. This pattern, however, could be interrupted by prayer. Therefore, knowledge of this pattern remained unreliable even though it was believed to be implanted in the believer's mind by God. Western distinctions between sensation, reason, and faith as ways of knowing became separations. Thus raising the question of their relationship.

The answer further illustrates how metaphysics has affected the dialogue via epistemology. According to the German philosopher Immanuel Kant (1724–1804), scientific knowledge of phenomena arises when sensations are organized by the mind using concepts such as space, time, and cause. Beliefs about nature become scientific knowledge if they correspond to phenomena. Since beliefs about God do not result from sensations they can be accepted only on faith. This separated scientific and religious knowledge into different categories so that no dialogue was possible between them. This separation became an issue in the engagement between religion and biology. The German anthropologist Johann Friedrich Blumenbach (1752–1840) used purpose as a natural secondary cause in explanations of animal development and saw God as the primary cause. For Kant, however, this meant that supernatural causes had been included in explanations of nature. That is, the religious belief that God had created things for a purpose had constituted a scientific explanation. Kant was willing to accept only the regulative use of purpose as a guide to research.

The existence of purposive behavior in organisms is described by a concept of goal or function that excludes from scientific explanation both divine and animal intent. It is used both to guide research (what is the function of venous valves?) and to explain the observations (the function of venous valves is to block reverse flow). In twentieth-century positivism, metaphysics and religion were denied the status of knowledge and meaning because their concepts were believed not to refer to sensible realities. However, Kant's separation and its positivistic interpretation failed for a variety of reasons. As a result, there is renewed interest in metaphysics, which has revealed that it often mediates between science and religion.

See also Dualism; Epistemology; Kant, Immanuel; Materialism; Naturalism; Nature; Ontology

Bibliography

brooke, john h. science and religion: some historical perspectives. cambridge, uk: cambridge university press, 1991.

brooke, john h.; osler, margaret j.; and van der meer, jitse m. eds. science in theistic contexts: cognitive dimensions. chicago: university of chicago press, 2001.

dhanani, alnoor. "islam." in the history of science and religion in the western tradition: an encyclopedia, ed. gary b. ferngren; edward j. larson; darrell w. amundsen; and anne-marie e. nakhla. new york: garland, 2000.

hull, david l., and ruse, michael, eds. the philosophy of biology. oxford: oxford university press. 1998.

kaiser, christopher b. creational theology and the history of physical science: the creationist tradition from basil to bohr. leiden, netherlands: brill, 1997.

lindberg, david c., and numbers, ronald l. god and nature: historical essays on the encounter between christianity and science. berkeley: university of california press, 1986.

mcmullen, emerson t. "anatomy and physiology to 1700." in the history of science and religion in the western tradition: an encyclopedia, eds. gary b. ferngren; edward j. larson; darrell w. amundsen; and anne-marie e. nakhla. new york: garland, 2000.

midgley, mary. science as salvation: a modern myth and its meaning. london and new york: routledge, 1992.

nasr, seyyed hossein. religion and the order of nature. new york and oxford: oxford university press, 1996.

qadir, c. a. philosophy and science in the islamic world. london and new york: routledge, 1988.

richards, robert j. "kant and blumenbach on the bildungstrieb: a historical misunderstanding." studies in the history and philosophy of biology and biomedical sciences 31 (2000): 11–32.

southgate, christopher; deane-drummond, celia; murray, paul d.; negus, michael r.; osborn, lawrence; poole, michael; stewart, jacqui; and watts, fraser. god, humanity, and the cosmos: a textbook in science and religion. edinburgh, uk: t&t clark, 1999.

van inwagen, peter. metaphysics. boulder, colo.: west-view, 1997.

jitse m. van der meer