Aristotle's account of phantasia in De anima, III, 3, occurs at a critical juncture of his inquiry into the nature and properties of the soul. Having just completed a long discussion of sensation (II, 5-III, 2), and wishing now to turn to a consideration of the power of thought (nous), which he regards both as distinct from and as analogous to sensation, he suggests that an explanation of phantasia is necessary at this point, since there is no thought without phantasia, just as there is no phantasia without sensation.1 But while this sketch of a complex dependency among the soul's cognitive powers makes clear the importance of phantasia and the need for some explanation of it, the intermediate place of phantasia in the discussion and the incidental way in which it is introduced are indications that Aristotle does not treat it for its own sake, but rather is compelled to turn to a consideration of it by the exigencies of the subject-matter at hand. The analysis of sensation, the characteristic power of animals, could, it seems, be adequately carried out with little reference to phantasia, even though Aristotle is elsewhere led to stress the closeness, and even, in some respect, the identity of these two powers; the discussion of thought, on the other hand, and specifically of the human thought which is Aristotle's concern in De anima, III, 4–8, apparently requires a special preliminary treatment of phantasia.