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The predicables (Gr. κατηγορούμενα) are the relations involved in saying something is one of many; they express the five basic ways in which one thing "can be said" of many as of a subject by way of formal predication. Such predication manifests a formal perfection of the subject; an otherwise unexpressed determination and is opposed to mere predicates of identity. The five predicables were enumerated in the third century by porphyry in his Introduction (Isagoge ) to the Categories of aristotle. They are the classic quinque voces: genus, species, difference, property and accident. The notions were examined at great length in medieval logic (see logic, history of).

Purpose. The predicables are used in the dividing of being into the ten supreme genera (Gr. κατηγορίαι, categories), which are divided and subdivided by specific differences that ultimately constitute the lowest species, the term of the process (see categories of being). Since the categories are drawn up in order to help in classifying and defining natural objects, it is obvious that the predicables also share this purpose. In a definition, several concepts, generic and differential, are ordered in such a way as to express distinctly the determinate kind of being of an object, thus setting it off sharply from other objects. Through the verbal formula that stands for these concepts, the mind knows a limited class of things with a peculiar identity. Thus it selects predicates that will set off a given class by its proper determinations. In the definitions sought, the whatness or quiddity (quod quid erat esse ) is known and expressed as the starting point of scientific knowledge.

Of the words used in formulating a definition, not all are equally effective. For example, an essential predicate will manifest the quiddity better than an accidental one. The several relations of these words to the subject being defined are called predicables. By an exhaustive division one discovers that there are five of these. Such words are predicable of a subject because they are first related to the subject, as a universal would look to its inferiors. Predicability presupposes that what is said of many is in some way in the many. Since predicability follows on universality as a necessary attribute, the relations of predicability correspond to the five relations of logical universality, wherein the mind recognizes the ways in which a nature, abstracted from singulars, may be found in them as in its inferiors (see universals).

Number and Definitions. The five predicables are attained in the following way: When something is said of a subject it can either (1) belong to the nature or essence of the subject and express its quiddity, or (2) belong to the subject in some other way beyond its essence, that is, as accidental to it. In the former case it will manifest either the whole nature or essence of the subject, or part of that nature. The predicable designating the whole nature is called species. The part of the essence that the subject has in common with other classes of things resembling it is called genus, or including class. The part that distinguishes the subject from all other classes is called the difference. In the latter case the predicate may indicate something outside the essence but necessarily following on it, the property; or may indicate something contingently associated with the subject, the predicable accident.

In the Isagoge the definitions follow in this order. Genus is the said universal of many differing in species, in answer to the question "What is it?" ("animal," of man and brute). Species is the universal said in answer to "What is it?" of many that differ only in number ("man," of Plato and Socrates). Difference is predicated as the qualitative part of the essence (in quale quid ) of those differing in number or also in kind ("rational," of man; "sensitive," of animal). Property is a universal said of a species as belonging only, necessarily and always to that species and its individuals ("able to speak," of man). Accident is a universal said of a species as belonging contingently to that species and its individuals ("white," of man).

The order in which the predicables are given reflects a proportionate share in the notion of universality. This is found more formally in essential predicates than in those that are outside the essence of the subject. And of the essential predicates, the generic are more universal than the specific, so that genus and species are given first as substantial predicates, then difference as a qualitative predicate, followed by property and accident as yet more distant from the essence of the subjects.

Predicates vs. Predicables. The predicables are distinct from the classes of predicates listed by Aristotle in the Topics (101b 11103b 19). In this treatise on dialectics, he sets out to classify problems concerning which arguments take place. Since dialectical reasoning inquires simply whether the predicate does or does not inhere in the subject in a given way (quia est ), these problems can be reduced to four relations that the predicate of a proposition may have to its subject. The division is made on the basis of essentiality of predicate to subject, and of convertibility of predicate and subject. There are four possible combinations: (1) definition (Gr. ρος)essential and convertible; (2) propertynonessential but convertible; (3) genus and generic differenceessential but not convertible; and (4) accidentnonessential and nonconvertible. Species is not listed separately because species is the subject of inquiry and not a predicate. Specific differences are tested in the same way as definition and may be reduced to it as a problem. Moreover, the question of specific difference is more proper to the specific science treating of the subject than to dialectics.

The division into classes of predicates is made so that the dialectician may discover the common means (loci ) for testing each kind of predicate. The predicables, on the other hand, follow on the several relations of one to many, of one nature in many inferiors that are immediately contained under the superior or universal. These inferiors may be singulars or other universals. Thus species and difference constitute distinct relations of universality to inferiors, but not classes of predicates or problems for the dialectician. Individuals enter as terms of the relation of universality, but not as subjects of dialectical propositions.

See Also: porphyrian tree; predication; intentionality; logic.

Bibliography: "Isagoge et in Categorias commentarium," Commentaria in Aristotelem Graeca, 23, ed. a. busse, (Berlin 18821909) 4.1. aristotle, Organon, tr. o. f. owen, 2 v. (London 18991900). h. b. veatch, Intentional Logic (New Haven 1952). p. coffey, Science of Logic, 2 v. (New York 1912; reprint 1938). i. m. bocheŃski, History of Formal Logic, tr. i. thomas (Notre Dame, Ind. 1961). boethius, In Isagogen Porphyrii commenta, ed. s. brandt (Vienna 1906). albert the great, Liber de Praedicabilibus, v.1 of Opera Omnia, ed. a. borgnet, 38 v. (Paris 189099). t. de vio cajetan, Scripta philosophica: Commentaria in Porphyrii Isagogen, ed. i. m. marega (Rome 1934). john of st. thomas, Cursus Philosophicus, ed. b. reiser, 3 v. (new ed. Turin 193037). john xxi, Petri Hispani Summulae logicales, ed. i. m. bocheŃski (Turin 1947).

[w. baumgaertner]