Metaphysics θ 3.

only so long as it is perceived or. as we say, only if it is "actually" being perceived. Thus, Aristotle concludes further. without the enactment of perception, such things as a colored thing and color, or a sonorous thing and tone would not be present. The variegated multiplicity of this immediate, sensually given world must start anew with each and every enactment of perception and then once again desist, so that what emerges and passes away there is itself nothing inherently present. Moreover, not only must the Megarians as a consequence of their thesis arrive at this conception of what is immediately and actually given, they must in general deny the possibility of a being that is in and of itself present, since this can be granted only with the acknowledgment that the being present of something that is perceptible does not remain singularly dependent upon the enactment of perception. In this way it turns out that the Megarian thesis in its implications goes much further still and grasps the essential conditions for the possibility of what is perceptible. It does not just appeal to the factically existent difference of each differently perceiving human. All the more so, then, and all the more certainly do the Megarians have to arrive at the teaching of Protagoras.

Aristotle thus pushes the Megarians and the implications of their thesis to a point which, as the invocation of Protagoras suggests, is just as much the dissolution of the possibility for truth as it is the dissolution of the self-reliant actuality of what is present; the latter is taken thereby to suggest that the currently discussed argument concerns the ἀψυχα. The actuality of what is present as the actuality of something self-reliant then still remains intelligible only if it can be shown that the actuality of what is perceptible as such does not lie in enactment of perception.

With this a task is posed which Aristotle does not positively resolve but rather exhibits in its inexorability. The entire subsequent history of philosophy. however. testifies to how little the solving of this task has met with success. The reason for this failure has little to do with not finding a way to an answer. but much more with the fact that continually and up until the present day the question as such has been taken too lightly. Here we will have to dispense both with unfolding this question in its many-sidedness and with showing thereby how

Martin Heidegger (GA 33) Aristotle's Metaphysics θ 1-3