 The impression that, from very early on, the interpreters were struggling to understand Aristotle is confirmed by the commentary tradition on the De anima. Consider, for example, De anima 3.5. There, Aristotle famously argues for the existence of an intellect that is separate, unaffected, and unmixed (De anima 430 a 17–18). In antiquity commentators traditionally referred to this intellect as the active (or productive) intellect, nous poiêtikos. Discussion on how exactly this intellect is to be understood started very early. There is evidence that already Theophrastus puzzled over it (Themistius, In De anima 110.18–28). Among other things, it is not obvious what sort of thing the active intellect is supposed to be. More directly, it is not clear whether it is a human or a divine intellect. What Aristotle says outside of the De anima is equally perplexing. In his work On the Generation of Animals Aristotle speaks of an intellect that enters “from without” (736 b 27). But it is not at all clear how the comment that Aristotle makes in this context is to be understood. What exactly is the status of this enigmatic intellect? How does it fit with the discussion offered in the De anima?