INDIVIDUATION

The constitution of a being whereby it is "undivided in itself and divided from all other beings" (Thomas Aquinas, Summa Theologiae 3a, 77.2; 1a, 29.4) or the constitution of a being "in such manner that it is not, according to the ratio by which it is called 'one,' communicable to many as to inferiors that would be subject to it or would, according to that ratio, be many" (F. Suárez, Disp. meta. 5.1.2). This article presents a philosophical analysis of this notion as it has been developed in the scholastic tradition. It consists of the following: (1) a clarification of the term "individuation"; (2) a historical survey of ancient and medieval views concerning it; (3) a summary of the teaching found in the writings of Thomas Aquinas and some of the most important Thomistic commentators; (4) a summary of the teaching of John Duns Scotus; and (5) a summary of the teaching of Francisco Suárez. (For other meanings of individuation, see individuality.).

Meaning of term. As is evident from the definitions cited above, two elements are involved in individuation, namely, indivision in self and division from every other individual. The negation of division involved in individuation is not, however, merely that which is found in unity in general. The negation of division proper to individuation involves denial of division of an entity into many, each of which would be the same as the entire entity divided. Thus, the undividedness of the individual or of a singular unity involves incommunicability; that is, whatever is an individual cannot be common either in the sense of actually existing in various things or in the sense of being predicable of many in the same manner.

Individuation may be considered in three ways: metaphysically, physically, and logically. These three ways of viewing individuation are distinguished by john of st. thomas in the following manner. Considered metaphysically, individuation means the last degree in the series of all predicaments or categories in the same way as the supreme genus means the first degree. This lowest degree is due to the ultimate difference by which a species is contracted to an individual. Considered physically, individuation means numerical unity, by means of which something is one in such manner that it is undivided in itself and divided from everything else. Considered logically, individuation means to be subjectable to all superior predicates and to be predicable of only one thing, that is, itself (Curs. phil. Nat. phil. 2.9.3).

The expression "principle of individuation" may be understood in various ways. The epistemological or manifestive principle of individuation is that by which one knows or recognizes an individual. This consists of the empirical signs of individuality, otherwise known as the individuating notes. The extrinsic principle of individuation is the efficient cause that produces the individual. The intrinsic principle of individuation is whatever entity it is within the individual that accounts for the individual's being this individual and no other. This intrinsic principle may be viewed, moreover, either as a formal principle or as a radical or constitutive principle. Accordingly, it may refer to that which formally constitutes the intrinsic completeness and extrinsic definiteness of every individual being; or it may refer to that from which arises, or by which is constituted, this individual—undivided in itself, incommunicable, and separated from all others.

Also, the principle of individuation may be viewed with reference to either absolute or relative individuality. Individuality is regarded absolutely when a thing is considered merely in itself, with no advertence as to whether or not there are or can be other members in the same species. Thus, every being may be considered individual in the absolute sense. Individuality is regarded relatively when a thing is considered in relation to an actual or at least possible multitude of things of the same species. Hence, only being that does not exclude the possibility of a plurality of beings of the same species may be considered individual in the relative sense.

Ancient and medieval views. The solution to the problem of the principle of individuation has importance not only in itself, but also for its consequences in many fields, such as metaphysics, epistemology, psychology, ethics, and philosophy of value. Hence, as would be expected, philosophers in all ages have been interested in this problem. However, since various philosophers have adverted to different aspects of this problem and, further, have based their solutions on different metaphysical and epistemological principles, the solutions that have been proposed are numerous and widely diverse.

Aristotle. aristotle proposed matter as the principle of individuation (Meta. 1034a 5–8, 1074a 33). From his Platonic legacy, he accepted the principle that scientific knowledge is immutable and eternally valid knowledge and that, therefore, the object of such knowledge must also be immutable and eternal. Holding both that scientific knowledge is knowledge of the essences of things and that things receive their essences from their forms, Aristotle concluded that the forms of things cannot be the basis for the multiplicity and change connected with individuals. Every difference of form would effect a specific difference (ibid. 1058b 1–2). However, matter, which the individual includes in addition to its form, is apt to function as the basis for multiplicity and change, for matter is potential and undetermined. Thus, there is nothing on the part of matter that prohibits the connection of the same form with various parts of the matter and thereby a multiplicity of individuals originating as the result of the divisibility of matter.

Boethius, Gilbert, and the Arabs. boethius asserted that "numerical difference is caused by a variety of accidents" (De Trin. 1). Thus, instead of explaining the individuation of an essence by completely undetermined matter, Boethius taught that an essence is individualized in virtue of its being determined by place, time, and other accidents. gilbert de la porrÉe maintained that the individual is constituted of various forms that are not themselves singular; yet in each individual there is something unique. This uniqueness he explained as arising from the uniqueness of the collection of forms composing the individual. Thus, though the forms themselves are common, that is, shared by other individuals in the same species or genus, the particular combination of forms in the individual is never duplicated in any other being (In librum de duabus naturis; Patrologia Latina 64: 1372D). The Arabian philosophers, such as alfarabi, avicenna, and averroËs, followed in general the Aristotelian doctrine that forms, universal in themselves, are individuated through matter.

Thirteenth-and fourteenth-century thinkers. Particularly during the thirteenth century there arose tremendous interest in the problem of individuation. In fact, solutions to this problem developed into programs distinctive of the various schools and consequently caused serious controversy. roger bacon placed great stress on the nobility and importance of the individual. In his youth, while lecturing on Aristotle's Metaphysics and writing his Quaestiones, Bacon did propose that individuation was derived principally from matter. In his later works, however, he presented an entirely different view, maintaining that there is no intrinsic cause of individuation since nothing can be added to a universal to make it an individual. It is God, he asserted, who causes individuals and therefore is ultimately responsible for individuation.

St. bonaventure, following the teaching of alex ander of hales, maintained that there is no form without matter. According to St. Bonaventure, however, matter may be either corporeal or spiritual, depending on the form it receives. Since matter is common to all beings, St. Bonaventure asserted that matter cannot be the source of individuation. Instead, he held that it is the union of the matter and form that is the true principle of individuation (In 2 sent. 3.1.2.3).

henry of ghent denied that individuality adds any real element to the existing specific essence. It is simply because individual things exist actually and extramentally that they differ from one another. Therefore, Henry asserted that individuation is explained by negation, namely, negation of intrinsic division and negation of identity with another being (Quodl. 5.8).

Most of the Franciscan thinkers of the thirteenth and fourteenth centuries, such as william de la mare, john peckham, Étienne tempier, richard of middleton, and John Duns Scotus, rejected, at times quite forcefully, the theory of matter as the principle of individuation. There were also, of course, many defenders of the Aristotelian theory, among whom may be enumerated albert the great, siger of brabant, giles of rome, and Thomas Aquinas.

For still other medieval philosophers, such as du randus of saint-pourÇain, peter aureoli, henry of harclay, and william of ockham, individuation presented no problem whatever. These philosophers, asserting that every being by reason of its actual existence is individual, found no meaning at all in the search for something whereby an extramental object is rendered individual.

Thomistic school. By far the most important of the defenders of the position that matter is the principle of individuation were St. thomas aquinas and his Dominican commentators, particularly Cajetan, John of St. Thomas, and Ferrariensis.

Aquinas's teaching. In accord with Aristotle, St. Thomas maintained that the form, which is the basis of the substantial essence, cannot be the basis of individuality; for form in itself is universal and can be received into one or more substrata. Also, accidents cannot account for individuality, for the individual belongs to the category of substance. Since the principle of individuation must then be substantial, but cannot be the form, which is a principle of specification, it follows that the principle of individuation must be matter. However, recognizing that primary matter, just as form, is by nature common and can be determined by many forms, St. Thomas introduced into his doctrine the notion of quantity. He proposed signate matter, matter related to quantity, as the principle of individuation (De ente 2). (see matter and form.)

This necessitated, however, an explanation of the precise relation of matter to quantity. In investigating the texts of St. Thomas with regard to this problem, one must consider these in their chronological order, for St. Thomas's thought on this subject underwent gradual evolution. In a very early work, influenced perhaps by Avicenna, he explained the diversity in matter by the forma corporeitatis (In 1 sent. 8.5.2). He quickly abandoned this position, however, and substituted in its place the notion of matter subject to indeterminate dimensions (In Boeth. de Trin. 4.2). Later, rejecting also this position, he maintained that matter with determined dimensions is the principle of individuation (De nat. mat. 3).

The individuation of human souls is explained by St. Thomas also by matter. He asserted that diversity and distinction of grades in souls is caused by diversity of bodies (In 2 sent. 3.2.2.3). Since the soul is according to its substance the form of a body, the soul necessarily retains its relation to the body, even after its separation from the body in death. It is by this relation to the body that St. Thomas explained the individuation of the separated soul. Further, since numerical difference comes about only by matter, it follows that where there is no matter beings cannot be multiplied within their kinds. Thus St. Thomas maintained that angels, in virtue of their having no matter, are infinite in the order of essence and therefore must differ specifically one from another (De spir. creat. 8).

Cajetan. Because St. Thomas did not clearly indicate in his writings the precise relation that matter bears to quantity in its role of principle of individuation, there arose considerable disagreement among his commentators. Tommaso de Vio cajetan, one of the principal interpreters of the thought of St. Thomas, rejected the opinion that the aggregate of matter and quantity is the principle of individuation. Rather, he maintained that matter itself is the proper root of individuation. In his commentary on De ente et essentia (5.37), Cajetan explained signed matter as matter capable of "this" quantity, so that it is not capable of "that." However, in his commentary on the Summa Theologiae (29.1), Cajetan modified his view slightly and explained signed matter as matter that is the source, the cause quasi-productive of the quantity. He argued that if quantity is able to accomplish its effect in things that receive it, surely the production of the same result should not be impossible to the fundamental source of quantity. Therefore, Cajetan asserted that matter is as capable as quantity of distinguishing numerically.

John of St. Thomas. John of St. Thomas held a similar opinion regarding the meaning of signed matter. He stated that the signation of matter is not accomplished by quantity as by an inherent form of matter affecting it, but by the intrinsic ordination of matter to quantity as to a dividing and separating form (Curs. phil. Phil. nat. 2.9.4). Just as matter implies an ordination to accidents as to dispositions by which the potentiality of matter is determined to this form rather than to that, so matter implies an ordination to quantity as to one of the dispositions. However, quantity has not only the function of informing the subject in which it is, thereby bestowing the formal effect of extension; but quantity is also related to its subject as dividing one part of matter from another part. Nonetheless, it is matter and not quantity that is the cause of incommunicability and substantial distinction.

Ferrariensis. An interpretation of signed matter that is very different from that presented by Cajetan and John of St. Thomas is found in the work of ferrariensis (francesco silvestri). According to him, signed matter is matter actually informed by quantity (Commentary on the Contra Gentiles 1.21). The fundamental reason on which he based his argument is that act is what distinguishes anything. Now signate matter is nothing other than matter so appropriated to a certain individual as to be capable of underlying that individual's quantity and no other. This appropriation, however, is either due to a form or not. If it is due to some form, either substantial or accidental, then the appropriated and signate matter does not imply only primary matter, but matter together with a form by which it is said to be appropriated and signate. If there is no form, then this situation must be reconciled with the fact that no potency whatever receives limitation and appropriation except by means of some act that it receives. Since primary matter is simply potency, it receives determination only from some form. Hence, if it is necessary that matter be signate in order that the form be individuated in virtue of this signation, then there must be in the matter some act that is really distinct from the matter.

Scotistic teaching. John Duns Scotus held that the principle of individuation must be a proper positive entity that is added to the nature and constitutes the individual. To determine the principle of individuation, Scotus considered two questions: (1) How is it that the individual is not divisible into subordinated parts? (2) How is it that the individual is really distinct from other individuals? His answer to the first question was based on the principle unum et ens convertuntur. He argued that an entity must correspond to every unity; and further, a different entity must correspond to a different unity. Since individuation is a special unity, there must be within the individual a corresponding entity. In answering the second question, Scotus asserted that the real distinction of individuals presupposes that there are contained in them realities that differ. Thus within the individual there must be, in addition to the common nature, a positive entity that corresponds to the singular unity and accounts for the distinctness of the individual. This positive entity, the haecceitas, which is formally distinct from the common nature, was likened by Scotus to the specific difference. He asserted that as the specific difference effects by its accession to the genus the indivisibility into further species and the distinctness of one species from all others, so the haecceitas effects by its accession to the species the indivisibility of the individual and the distinctness of one individual from all others (Op. oxon. 3.6.9).

Suárezian teaching. A position very different from both that of St. Thomas and that of Scotus is found in the work of Francisco suÁrez. Admitting nothing in reality that is not actually singular, Suárez found no need for a principle of individuation for an individual substance other than the entity of the substance itself. Thus he writes that "every entity is by itself the principle of its individuation" (Disp. meta. 5.6.1). Although Suárez admitted that individual unity does add something to the common nature, he insisted that what the individual unity adds is only mentally distinct from the nature (5.2.16). The individuation of all finite being, whether spiritual or material, is explained in the same way by Suárez. Further, with this explanation of individuation, it does not follow necessarily that purely spiritual creatures are specifically different; for similarity does not exclude distinctness.

See Also: essence.

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[j. r. rosenberg]