moving by volition, rational—or even laughing—then every one of those predicates is itself a conceived meaning and enters into the total conception. Likewise, if he pictures a “rational animal,” both “animal” and “rational” are parts of what he has conceived and fall within it. Whatever necessarily attends that mental image—such as being alive, sentient, and growing—remains necessarily attached to the conception in the mind. Hence the quiddity corresponds to what a term signifies by complete conformity; its constitutive part, an essential attribute included within it, corresponds to what the term signifies by inclusion; and the property that is necessary to it yet external to it corresponds to what the term signifies by implication. Clearly all of this merely follows the individual’s mental conception, whether that conception matches external reality or not; it does not arise from the realities themselves.
The root of their error is that they have confused what exists in the mind with what exists outside it. When someone defines man, for example, as “a body that is alive, sentient, growing, moves by choice, and is rational,” the statement is composed of words and meanings: each word carries one of those meanings, and every meaning forms a part of the overall statement.
As for his third point—that “all the differentiae must be listed”—this is like requiring that the genus itself be listed: neither condition helps to depict the essence, while the needed distinction can be achieved without them. It is nothing but a convention. The scholastic theologians (mutakallimūn) agree that it is impermissible to couple two attributes that are co-extensive in their scope, contrary to what these logicians demand; therefore two differentiae are not to be combined. Thus, if one defines “animal” as “a body that is growing, sentient, and moves by volition,” “sentient” and “moving by volition” are two differentiae. The logicians insist on mentioning both, whereas the theologians forbid combining them and require one to suffice.
Regarding the fourth aspect, it belongs to the same category, for it substitutes a remote genus for the proximate; for dividing