Aristotle introduces the assumption that mind is, as described by Anaxagoras, 'without mixture,' later restating it in his own terms as the view that mind is simple and ἀπαθές and without anything in common with anything else. This leads to two aporias: how, Aristotle asks, will thinking be possible under the assumptions stated, and how can mind itself be an object of thought? He then states two theses of his own: while mind is its objects potentially it is nothing in actuality until thinking occurs, and in the case of things without matter what thinks is the same as what is thought. But what is the fate of the Anaxagorean assumption in the resolution? That is the topic of this paper.
Driscoll, John, "The Aporias of De Anima Γ 4, 429b22-430a9." (1987). The Society for Ancient Greek Philosophy Newsletter. 144.