Aristotle has just finished explaining the four different categories of topics that we could speak on. There was definition, property, genus and accident. Now he will make some concluding remarks and tell us what this means for our study of dialectic. He does this in Topics, Book 1.
We must not fail to observe that everything applicable to property and genus and accident will be applicable to definition as well. For when we have shown that the content of the definition fails to belong to the subject alone, as we do in the case of a property, or that the genus rendered in the definition is not the true genus, or that any of the things mentioned in the phrase used does not belong, as would be remarked in the case of an accident, we shall have demolished the definition- so that, in the sense previously described, all the points we have enumerated might in a way be called definitory. But we must not on this account expect to find a single line of inquiry which will apply universally to them all- for this is not an easy thing to find, and, even were one found, it would be very obscure indeed, and of little service for the treatise before us. Rather, a special plan of inquiry must be laid down for each of the classes we have distinguished, and then, starting from what is appropriate in each case, it will be easier to make our way right through the task before us. So then, as was said before, we must outline a division of our subject, and other questions we must relegate each to the particular branch to which it most naturally belongs, speaking of them as definitory and generic questions. The questions I mean have practically been already assigned to their several branches.
Everything that Aristotle has said about property, genus and accident will be applicable to definition as well. If we show that the definition applies to something other than the subject then we have shown that it is not the right definition. This is the same way that we show that a supposed property is not a property at all. This will also be true if we show that the genus in the definition is the wrong genus or that the definition contains an accident. However dialectics might be unified in our discussion of definition, there is no common procedure to be found for all kinds of arguments. Even if we did find such a procedure, it would be obscure and likely useless. So it would be much better to divide dialectics into four parts: definition, property, genus and accident. We will ask how to investigate each kind of discussion one at a time. So all of the questions that we have will first be organized into one of these four kinds and then they will be answered in the way that we answer questions of that kind.
Next, Aristotle will discuss sameness and difference.