It is supposed (ad hominem) that the potential intellect is eternal. -- Yet somehow the argument here seems to miss the point. The Commentator never said that the presentations in the eternal potential intellect depended on the phantasms of any individual. He never likened those presentations to the individual's fleeting visual impressions of things: but he likened the presentations in the eternal intellect to things, and the phantasms of the individual to his visual impressions of things. Averroes contended that 'forms,' or aspects of things, exist in two ways, in both eternally: (a) materially, in sensible things, the world being eternal, in which sensible things these forms are potentially intelligible, being abstracted thence by intellect: (b) intellectually, in the eternal intellect, which is at once potential and active. He added that the same forms had an intellectual existence in a third way, namely, a temporal existence in the mind of this and that individual, which mind is 'continued,' or 'conjoined' for a time with the eternal intellect: this asserted 'continuation' of the temporal with the eternal is the theme of contention between Averroes and St Thomas.
St Thomas might refit his argument (as indeed he does presently) by demanding how intellectual presentations come to be in this supposed one eternal intellect, whether by abstraction from previous phantasms or not. To say that the potential intellect had impressions independent of previous phantasms, would put the Commentator in flat contradiction with Aristotle; e.g., De anima, III, vii, 3, 4: "To the intellectual soul phantasms are as sense-perceptions: wherefore the soul never understands without a phantasm." On the other hand, if phantasms are presupposed, there must have been phantasms also from eternity: how otherwise could an eternal mind depend on phantasms for all its content?
Of God and His Creatures: 2.73