Abstract

The chief virtue of Aristotle' s theory of definition, as presented in the Posterior Analytics, Topics, Metaphysics, De Partibus Animalium, and elsewhere, is that it takes into account the full meaning of the question, "What is X?"--especially when asked about natural entities. This is because his theory recognizes the crucial distinction presupposed in asking it, namely, between first identifying the X and ultimately explaining it. Those modern philosophers for whom definitions are merely conventional ways of identifying the definiendum ignore the explanatory role of definition. ;For Aristotle, proper scientific definition of a natural entity involves first identifying it by means of its properties; but it also provides the single explanation that accounts for all these properties. Thunder, for example, is not simply "a certain noise in clouds"; it is a certain noise to be accounted for by a certain explanation. This can no more be simply a matter of convention than can any scientific explanation: in fact, there is an internal necessity to such a definition, which is in effect an explanatory story. ;Finding the correct explanatory definition for an item depends on correctly classifying it, and thus indicating the correct level of generality to which the explanation applies. In accounting for all the identifying properties of the item's class, the explanatory definition, in turn, shows the class to be a true natural kind, rather than an arbitrary grouping . ;The identification/explanation distinction coincides with two more fundamental ones: between existence and essence, and between particular and universal. This can be seen in the discussion in Posterior Analytics II.8-10 of the demonstration that "manifests" a definition. This demonstration is best understood as a chain of two types of syllogisms, the first providing the explanation for a universal essence, the second serving to identify what is being explained in a particular existing entity. ;This identification/explanation distinction can be also seen in the discussion of matter and form in the Metaphysics. In Metaphysics Z Aristotle argues that definition must in some way include mention of matter: the full definition of humanity must include the ultimate explanation of all the material properties by which one correctly identifies human beings. Form, in turn, is meant to be provide that explanation, showing why this mass of flesh and bones is a human being