anagkê ara epei panta noei, amigê einai hina geôrizê: paremphainomenon gar kôluei to allotrion kai antiphrattei dio oude memichthai eulogon auton tô sômati (For since it understands all, it must be unmixed with any, in order to know: for any strange element coming in besides acts as an obstacle and a barrier to knowledge; therefore it is reasonable that it should not be mixed up with the body). -- De anima, III, iv, 3, 4.

Of God and His Creatures: 2.59