At Ph. 3.4, Aristotle begins his discussion of the Unlimited. As is customary with him, a preliminary to the investigation proper is set up: he presents and discusses other thinkers' opinions on the subject, from which to draw indications on the meaning—and possibly the existence—of the entity at issue. As for the question of what the Unlimited is, Aristotle points out that there is a complete agreement on two points: the Unlimited pertains to physics, and it presents itself as a principle of sorts. A matter of disagreement concerns the categorial status of the Unlimited: Plato and the Pythagoreans regard it as something existing per se, whereas the Physicists claim that it is only the attribute of something else. A concise exposition of these theories follows.