In his own De anima , Alexander of Aphrodisias famously identifies the “active” ( poietikon ) intellect with the prime mover in Metaphysics Λ. However, Alexander’s claim raises an issue: why would this divine intellect come in the middle of a study of soul in general and of human intellection in particular? As Paul Moraux asks in his pioneering work on Alexander’s conception of the intellect, is the active intellect a “useless addition”? In this paper, I try to answer this question by challenging a solution according to which the active intellect would intervene directly with the material intellect to trigger its ordinary working. I argue that the active intellect acts as a final cause, both for human intellect and for its ordinary objects of thought. The active intellect is twice “cause of the intellection”, i.e . cause of the actualization of human thought: once (i) when it offers thought occasions for thinking through objects, and again (ii) when it actualizes mediately the human intellect itself in its development. This reading agrees with Alexander’s usual position about the prime mover’s causality. It accounts for the multiplicity of expressions with which Alexander describes the causality of the active intellect in his De anima . It also explains why the development of human intellect has been described without direct reference to active intellect, since substances do not aim directly at the First cause, but their aiming at it is mediated by their desire for their own good.