Such is the number of the works written by [Aristotle]. And in them he puts forward the following views. There are two divisions of philosophy, the practical and the theoretical. The practical part includes ethics and politics, and in the latter not only the doctrine of the state but also that of the household is sketched. The theoretical part includes physics and logic, although logic is not an independent science, but is elaborated as an instrument to the rest of science. And he clearly laid down that it has a twofold aim, probability and truth. For each of these he employed two faculties, dialectic and rhetoric where probability is aimed at, analytic and philosophy where the end is truth; he neglects nothing which makes either for discovery or for judgement or for utility. As making for discovery he left in the Topics and Methodics a number of propositions, whereby the student can be well supplied with probable arguments for the solution of problems. As an aid to judgement he left the Prior and Posterior Analytics. By the Prior Analytics the premisses are judged, by the Posterior the process of inference is tested. For practical use there are the precepts on controversy and the works dealing with question and answer, with sophistical fallacies, syllogisms and the like.
Diogenes Laertius, Lives of the Philosophers, "Aristotle", Book V.28-29. This is an early form of a view of Aristotle's logical works that would become central with the Islamic commentators.
