 Though Alexander follows the Aristotelian texts quite conscientiously, he often concentrates on special points and the respective passages while passing over others with brief remarks. Thus in his comments on the first book of Aristotle’s Metaphysics he devotes more than half of his exegesis to the two chapters in which Aristotle attacks Plato’s theory of Forms (Metaph. A, 6 &amp; 9). Since Aristotle there focuses on Plato’s attempt to connect the Forms with numbers, a theory that is not elaborated in the dialogues, Alexander’s disquisition turns out to be our most valuable source on the vexed question of Plato’s Unwritten Doctrine and also on the impact of this doctrine on the members of the Early Academy (see Harlfinger &amp; Leszl, 1975; Fine 1993). Though on the whole Alexander adopts Aristotle’s critical stance towards Plato’s separate Forms, he sometimes at least indicates the possibility of dissent. When, for instance, Aristotle claims that Plato recognizes only two of his own four causes, the formal and the material cause, Alexander refers to the demiurge’s activities in the Timaeus as an example for an efficient cause acting for the sake of a final cause. But then he adds a justification to explain why Aristotle acknowledges neither of the two causes in his report on Plato (59,28–60,2): “The reason is either because Plato did not mention either of these in what he said about the causes, as Aristotle has shown in his treatise On the Good; or because he did not make them causes of the things involved in generation and destruction, and did not even formulate any complete theory about them.”