Aristotle - Organon: Topics (2)

The same remark applies to the theory of the proposition which is the basis of Aristotelian logic. By asserting that every proposition is composed of a subject and an attribute, Aristotle supported a thesis of immense scope, not only logically, but also metaphysically. Now, this thesis, he borrows it not from the analysis of language as has sometimes been said (and in fact, he knows verbal forms, such as those of the wish, of the prayer, which he refers to rhetoric), but rather from the analysis of dialectical problems. Indeed, every dialectical problem consists of asking whether an attribute belongs or not to a subject; it is by contesting that it was possible to affirm an attribute of a subject that the antilogics made dialectics impossible; Conversely, it was the needs of dialectics that led Aristotle to his theory, and this is why he usually states propositions not in the form that has become classical, A is B, but in this one: B belongs to A. A proposition is a protasis, that is to say, an affirmation that one presents for the approval of an interlocutor. The same is true of the classification of propositions; the classical division into universal (affirmative or negative) and particular (affirmative or negative) propositions presents itself first as a division of problems; every problem consists in fact in asking whether an attribute belongs (or does not belong) to the whole (or to a part) of a subject, which gives the formula of the four propositions[1].

Furthermore, in order to grasp the scope of a dialectical problem, it is important to know the genus of the attribute that is being asked. Does the attribute say what the subject is, or does it only state a property of the subject? Does it state a property that belongs to it necessarily, or only accidentally? So many cases must be distinguished to make discussion possible; for many errors arise from the fact that one believes oneself entitled to reverse propositions, that is, to admit, because A belongs to all B, that B belongs to all A. Now, this reversal is only admissible if A is a proper of B, that is, belongs to it necessarily and exclusively. From concerns of this kind, we see the birth of the famous distinction of attributes into five classes: genus, species, difference, proper, and accident[2]. The first three are obviously linked to the Platonic practice of division; The division was intended to show what a subject is (or its quiddity) by first determining the most general class of which it was a part, then by dividing this class into several; the broadest class (animal) becomes in Aristotle the genus; what allows one to separate subordinate classes are differences (reasonable); the synthesis of genus and difference is the species (man); and each of these three attributes, in Aristotle as in the Platonic division, answers the question what is? the genus and the difference indicating, each taken separately, a part of the essence of the species, and taken together, this entire essence, of which the formula is the definition. The proper and the accident, on the contrary, are attributes which are not part of the essence of the subject, that is to say do not answer the question what is? But the proper is a necessary dependence on the essence of the subject, to which it belongs exclusively, just as the equality of angles to two right angles belongs to the only triangle among polygons; the accident may, on the contrary, not belong to the subject.