The face of the divine: Pure form according to Alexander of Aphrodisias

In his De anima, Alexander of Aphrodisias identifies the active intellect with the first mover and describes this first cause as an immaterial and separate form. This article aims at explaining to what extent, and why Alexander differs from Aristotle on this point. Aristotle never defines the first mover as a form: he claims that its being is actuality. How could Alexander, who became famous as the Commentator par excellence, assert a thesis that seems so dangerously close to Platonism? I intend to show that this description of the first mover as a pure "visage" (eidos) is not an accident in Alexander's thought and that it is linked up with his epistemological conceptions as well as with his metaphysics.