Chapter 4
Those which have already been stated, and also the others from cases and conjugates, are the most appropriate places; wherefore we ought especially to retain these, and to have them at hand, since they are most useful to the greatest number (of problems). Of the rest also, those which are especially common, for these are the most efficacious of the remaining ones; as, for instance, to regard singulars, and to consider in species, whether the definition is suitable, as species is synonymous. Such however is useful against those who lay down that there are ideas, as was before observed; moreover, whether a name is introduced metaphorically, or whether the same thing is predicated of itself as different, and if there be any other place common and efficacious, we must employ it.
Chapter 5
That it is more difficult to confirm, than to subvert definition, is evident from what will next be said, since it is not easy for him (who interrogates) to perceive and take from those who are interrogated, propositions of this kind; as that of the things in the assigned definition, one is genus, but another difference, and that genus and differences are predicated (in reply) to what a thing is. Still without these there cannot possibly be a syllogism of definition, as if certain other things also are predicated of a thing, in respect of what it is, it is dubious whether what is stated, or something else, is its definition, since definition is a sentence signifying what is the very nature of a thing. Now it is evident from what follows, for it
