Book II, Chapter 13 of the Posterior Analytics begins, “Now we have already said how what a thing is is set out in the terms, and in what way there is or is not demonstration or definition of it; let us now say how one should hunt out what is predicated in what a thing is.” That the hunt for what belongs to a thing in what it is does not differ from a hunt for the demonstrative middle is not immediately obvious, but follows from the fact that what belongs in what a thing is does not differ from what is necessary. The discussion which follows makes clear that the hunt here has the purpose of discovering what something is, that is, of finding out of the demonstrative middle what it is. The things which are predicated in what it is are hunted out, sorted, and sifted with a view to the substance of the object. Aristotle says this explicitly: “such things must be taken up to the first point at which just so many are taken that each will belong further but all of them together will not belong further; for necessarily this will be the substance of the object.”
The question about how things predicated in what it is are to be hunted out is not a question of by what means these things may be identified. Rather it is a question of the context proper to such a pursuit: “How?” here has the sense of “In what way? Along what path?” None of these attributes inhering necessarily in a thing is of scientific interest on its own account, as the stopping point of an inquiry. Rather, they have the character of an “if it is.” Knowledge of them imparts knowledge that there is a demonstrative middle. The satisfaction of the inquiry in pursuit of the that is not a stopping point, but opens on a further inquiry, in pursuit of what it is. Aristotle is not here articulating a methodology for turning up attributes which belong necessarily to something. Indeed, his position here would caution against the very notion of such a methodology in abstraction from inquiry proper, which directs itself to a middle term to learn what it is. Such a pedantic, disinterested manner of “hunting out” would differ from the “hunting out” here recommended as a sportsman's weekend out putting bullets in things differs from the patient, urgent incursions into the wild of a man who hunts for his sustenance. That is to say, it differs in failing, however many trophies it may accrue, to be the hunt—the genuine, high human activity of science which runs through and unifies our intellectual capacities, and gives them their meaning.