Time: Religious and Philosophical Aspects

According to Augustine of Hippo (354–430) time cannot be satisfactorily described using one single definition. In his words: "What, then, is time? If no one asks me, I know: if I wish to explain it to one that asketh, I know not" (Confessions 11, c. 14). The attempt to establish a conclusive definition of time ultimately leads to confusion. Time is not definable by any other concepts. Time, in its fullness, is unique and sui generis. This view is now generally accepted among philosophers of time. No attempt to clarify the concept of time is claimed to be more than an accentuation of some aspects of time at the expense of others. The statement of Plato (428–347 b.c.e.) that time is the "moving image of eternity" and Aristotle's (384–322 b.c.e.) suggestion that "time is the number of motion with respect to earlier and later" are no exceptions.

Time and eternity

Many philosophical and religious schools have assumed that no beginning or end can be attributed to time. For instance, in Indian thought the universe is largely conceived as undergoing repeated creation and dissolution. According to this cosmological model, each world-cycle has to be measured in terms of billions of humans years (Balslev, p. 140 ff.). Ancient Greek thought includes the even stronger idea of cyclic time according to which not only the cosmological processes but all individual destinies are repeated in every detail in time (Whitrow, p. 14 ff.). Jewish, Christian, and Muslim philosophers have had to reject this idea of cyclic time because it leaves no room for genuine progress or final salvation. Augustine, in particular, was very clear about this: "Heaven forbid, I repeat, that we should believe that. For Christ died once for our sins, but rising from the dead he dies no more, and death shall no longer have domain over him" (De Civitate Dei 12; vol. 4, p. 63)

Some Muslim thinkers such as al-Farabi (873–950) and Avicenna (980–1037) held that the act of creation should be conceived as atemporal and purely logical. In Judaism and Christianity, however, most philosophers have rejected this view maintaining that God's creation of the world was in fact its temporal beginning. In Judaic thought some have argued that time existed and the Torah was created before the creation of the world. This view of time would allow the notion of the universe being created in time. However, according to the most common view in traditional medieval philosophy, time is considered to be relational; that is, there can only be time in relation to a world of events. With this view of time, creatio ex nihilo means that the universe does not owe its existence to anything in the physical world, and it can only be explained by reference to something that is not a part of this temporal world. The idea of the absolute beginning of the universe does not imply any change from one state to another.

Medieval writers typically held that time itself began with creation. Thomas Aquinas (c. 1225–1274) stated this view in the following way: "The phrase about things being created in the beginning of time, means that the heavens and earth were created together with time" (Summa Theologica 1a, 46, 3). A similar view had been expressed earlier by the great Jewish scholar Moses Maimonides (1135–1204), according to whom the biblical statement of God's existence before the creation of the world has to be interpreted in terms of a "supposition or imagination of time" (Sorabji, p. 237). In the same vein, Aquinas stated:

God is before the world by duration. The term 'duration' here means the priority of eternity, not of time. Or you might say that it betokens an imaginary time, not time as really existing, rather as when we speak of nothing being beyond the heavens, the term 'beyond' betokens merely an imaginary place in a picture we can form of other dimensions stretching beyond those of the body of heavens. (Summa Theologica 1a, 46, 1)

This means that God's eternity should not be understood as some sort of everlasting existence of the same kind as human existence. God's eternity is a dimension other than that of human time. For this reason the biblical statement that God is before creation should not be understood in a temporal way. It must be admitted, however, that it seems almost impossible to clarify this nontemporal use of before, although "logically before" must be a part of the meaning. But if the reality of a spiritual world is accepted, it is certainly likely there are relations that cannot be fully explained or understood by human beings.

Aquinas compared this view with the relation between the center and the circumference of a circle. The relation between the center and the circumference is the same all the way round; in a similar manner, God relates in the same way to all times.

Furthermore, since the being of what is eternal does not pass away, eternity is present in its presentiality to any time or instant of time. We may see an example of sorts in the case of a circle. Although it is indivisible, it does not co-exist simultaneously with any other point as to position, since it is the order of position that produces the continuity of the circumference. On the other hand, the center of the circle, which is no part of the circumference, is directly opposed to any given determinate point on the circumference. Hence, whatever is found in any part of time coexists with what is eternal as being present to it, although with respect to some other time it be past or future. (Summa contra gentiles 1, c. 66)

The reality of the tenses

Since antiquity two images of time have been discussed: the line made up of stationary points and the flow of a river. Philosophically speaking, these images correspond to two positions: "being as timeless" and "being as temporal." The two positions can be found in early Indian thought, for instance, as held in Brahmanism and Buddhism, respectively. The different schools in the Brahmanical tradition have maintained that the ultimate being is timeless (i.e., uncaused, indestructible, beginningless, and endless). Buddhists, on the other hand, have claimed that being is instantaneous and that duration is a fiction since according to their view a thing cannot remain identical at two different instants (Balslev, p. 69 ff.).

In classical Greek thought the tension between the dynamic and the static view of time has been expressed, for example, by the Aristotelian idea of time as the number of motion with respect to earlier and later—an idea that comprises both pictures. On the one hand time is linked to motion (i.e., changes in the world), and on the other hand time can be conceived as a stationary order of events represented by numbers. This discussion is also reflected in Isaac Newton's (1642–1727) ideas of time, according to which absolute time "flows equably without relation to anything external" (Principia, 1687).

The basic set of concepts for the dynamic understanding of time are past, present, and future. After J. M. E. McTaggart's analysis of time in "The Unreality of Time" (1908), these concepts (i.e., the tenses) are called the A-concepts. They are well suited for describing the flow of time, since the present time will become past (i.e., flow into past). The basic set of concepts for the stationary understanding of time are before, simultaneously, and after. Following McTaggart, these are called the B-concepts, and they seem especially apt for describing the permanent and temporal order of events.

Philosophers discuss intensively which of the two conceptions is the more fundamental for the philosophical description of time. The situation can be characterized as a debate between two Kuhnian paradigms: the ideas embodied by the well-established B-theory, which were for centuries predominant in philosophical and scientific theories of time, and the rising A-theory, which in the 1950s received a fresh impetus due to the advent of the tense logic formulated by Arthur N. Prior (1914–1969). Still, many researchers do not want to embrace the A-conception. According to A-theorists, the tenses are real, whereas B-theorists consider tenses to be secondary and unreal. According to the A-theory the "Now" is real and objective, whereas the B-theories consider the "Now" to be purely subjective.

Following the ideas of Aquinas, some argue that time from God's perspective should be understood in terms of B-concepts because time is given to God in a timeless way. But it should be mentioned that Aquinas also maintained that divine knowledge can be transformed into the temporal dimension by means of prophecies. It seems that Aquinas was suggesting a distinction between time as it is for temporal beings such as humans and time as it is for God, who is eternal. However, this does not answer the important question: Are the tenses real? Is the "Now" real?

Most writers in Christian philosophy defend the view that "my Now," "my present choice," or "my present awareness" actually represents something real. This will lead most writers in Christian philosophy to the A-theory. They normally find it obvious that the concept of time has to be related to the human mind. Therefore it becomes more natural to describe time by means of tenses (past, present, and future) than by means of instants (dates, clock-time, etc.). With tenses, one can express that the past is forever lost and the future is not yet here. Without these ideas one cannot hope to grasp the idea of the passing of time. Phenomena such as memory, experience, observation, anticipation, and hope are all essential for the way time is understood. Notions of past and future time, the interpretation of the past, and expectations of the future are all interwoven in the human mind. Nevertheless, A-theorists claim that the distinction between past and future is objective, or at least intersubjective.

Human freedom and divine foreknowledge

During the Middle Ages logicians felt that they had something important to offer with regard to solving fundamental questions in theology. The most important question of that kind was the problem of the contingent future. The intellectuals of the Middle Ages saw the problem as intimately connected with the relation between two fundamental Christian dogmas: human freedom and God's omniscience. God's omniscience is assumed to comprise knowledge of future choices to be made by human beings but apparently gives rise to a straightforward argument from divine foreknowledge to necessity of the future: If God already knows the decision one will make tomorrow, then there is already now an inevitable truth about one's choice tomorrow. Hence, there seems to be no basis for the claim that one has a free choice, a conclusion that violates the dogma of human freedom. The argument proceeds in two phases: first from divine foreknowledge to necessity of the future, and from that argument to the subsequent conclusion that there can be no real human freedom of choice. The problem obviously bears on the theological task of clarifying questions such as "In which way can God know the future?" or "What is to be understood by free will and freedom of choice ?" In his treatise De eventu futurorum, Richard of Lavenham (c. 1380) suggested a systematical overview of basic approaches to the problem: If two dogmas are seemingly contradictory, then one can solve the problem by denying one of the dogmas or by showing that the apparent contradiction is not real (Øhrstrøm and Hasle, p. 87 ff.).

Denial of the dogma of human freedom leads to fatalism (first solution). Denial of the dogma of God's foreknowledge can either be based on the claim that God does not know the truth about the future (second solution) or the assumption that there is no truth about the contingent future since nothing has yet been decided (third solution). One can alternatively demonstrate that the two dogmas, rightly understood, can be united in a consistent way (fourth solution). The first two solutions were seen as contrary to Christian belief, according to which humans are free at least to a certain degree, and according to which God knows all truth. Peter Aureole (c.1280–1322) is notable among the defenders of the third solution. He claimed that neither the statement "the Antichrist will come" nor the statement "the Antichrist will not come" is true, whereas the disjunction of the two statements is actually true. From that point of view, one can naturally claim that the dogma of God's omniscience is still tenable, even if God does not know if the Antichrist will come or not. God knows all the truths given and cannot know if the Antichrist will come due to the simple reason that no truth about the Antichrist's future decisions yet exists. In modern philosophy, this third solution has been defended by Prior and by Charles Sanders Peirce (1839–1914). This idea of a totally open future is often illustrated using a branching time model:

The central feature of the fourth solution is its use of the notion of a "true future" among a number of possible futures. This solution was originally formulated by William of Ockham (c. 1284–1347). He discussed the problem of divine foreknowledge and human freedom in his work Tractatus de praedestinatione et de futuris contingentibus. He asserted that God knows all future contingents, but he also maintained that human beings can choose between alternative possibilities. Ockham was aware that considerations on the communication from God to human beings are essential. God can communicate the truth about the future to human beings. Nevertheless, according to Ockham, divine knowledge regarding future contingents does not imply that they are necessary. As an example, Ockham considered the prophecy of Jonah: "Yet forty days, and Nineveh shall be overthrown" ( Jonah 3:4). This prophecy is a communication from God regarding the future. Therefore, it might seem to follow that when this prophecy has been proclaimed, then the future destruction of Nineveh is necessary. But Ockham did not accept that. Instead, he made room for human freedom in the face of true prophecies by assuming that "all prophecies about future contingents were conditionals" (Ockham, p. 44). So, according to Ockham, the prophecy of Jonah must be understood as presupposing the condition "unless the citizens of Nineveh repent." Obviously, this is exactly how the citizens of Nineveh understood the statement of Jonah.

Ockham realized that the revelation of the future by means of an unconditional statement, communicated from God to the prophet, is incompatible with the contingency of the prophecy. If God reveals the future by means of unconditional statements, then the future is inevitable, since the divine revelation must be true. The concept of divine communication (revelation) must be taken into consideration, if the belief in divine foreknowledge is to be compatible with the belief in the freedom of human actions. However, Ockham had to admit that it is impossible to express clearly the way in which God knows future contingents. He also had to conclude that, in general, divine knowledge about the contingent future is inaccessible. God is able to communicate the truth about the future to human beings, but if God reveals the truth about the future by means of unconditional statements, the future statements cannot be contingent anymore. Hence, God's unconditional foreknowledge regarding future contingents is in principle not revealed, whereas conditionals can be communicated to the prophets. Even so, that part of divine foreknowledge about future contingents, which is not revealed, must also be considered as true according to Ockham.

It can be argued that Anselm (1033/34–1109) had suggested long before Ockham a similar solution to the problem of divine foreknowledge and human freedom. Much later, Gottfried Wilhelm Leibniz (1646–1716) worked out a metaphysics of time, which from a systematical point of view is similar to the thoughts of Anselm and Ockham. The Ockhamistic solution can be illustrated using the modern notion of "branching time":

From a theological point of view this model presupposes what has been called middle knowledge, which is God's knowledge of what every possible free creature would do under any possible set of circumstances (Craig, p. 127 ff.).

Toward a common language for the study of time

In order to gain more knowledge about the temporal aspects of reality, time has to be studied within many different strands of science. If such studies are to lead to a deeper understanding of time itself, various disciplines have to be brought together in the hope that their findings may form a new synthesis, even though one should not expect any ultimate answer regarding the question of the nature of time. If a synthesis is to succeed, a common language for the discussion of time has to be established.

The twentieth century has seen a most striking rediscovery of the importance of time and tense. This is first and foremost due to the work of Arthur Prior, who was deeply inspired by his studies in ancient and medieval logic. During the 1950s and 1960s Prior laid out the foundation of tense logic and showed that this important discipline was intimately connected with modal logic. He revived the medieval attempt at formulating a temporal logic corresponding to natural language. In doing so, he also used his symbolic formalism for investigating the ideas put forward by these logicians. Prior argued that temporal logic is fundamental for understanding and describing the world in which human beings live. He regarded tense and modal logic as particularly relevant to a number of important theological as well as philosophical problems. The main parts of temporal logic have been developed using mathematical symbolism and calculus, but nevertheless it has first and foremost been a philosophical enterprise.

According to Augustine, all humans have a tacit knowledge of what time is, even though they cannot define time. In a sense, the endeavor of temporal logic is to study some manifestations of this tacit knowledge. The concept of time can in fact be studied using temporal logic. It seems likely that Prior's tense logic may become a crucial part of a common language for the discussion of time.

In his temporal logic Prior, among many other things, took the uncertainty of the future into account. This means that it is assumed that no description of the future can be complete because it must be discussed in terms of open statements and ambiguous expressions. The reason is that some future events cannot be specified fully and satisfactorily in terms of the present vocabulary. In his temporal logic Prior suggested a notion of unstatability. According to this idea, the language needed for a proper description of the temporal world is growing, and present events can be described more fully than was possible earlier when the events were still part of the future.

See also T = 0; Time: Physical and Biological Aspects

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peter ØhrstrØm