Of all the Aristotelian doctrines perhaps the most difficult is that concerning the Active and Passive Intellects which we find in the short fifth chapter of the third book of the De Anima. Interpretations of this chapter have been almost as numerous as interpreters, and it would be naive to expect at this stage to be definitive. Nevertheless it seems that progress has been delayed in many cases by a too casual approach to what Aristotle says in the chapter itself - and this at least admits of some improvement.
Rist, John M., "Notes on Aristotle De Anima 3.5" (1963). The Society for Ancient Greek Philosophy Newsletter. 444.