 The attempt to ‘naturalize’ crucial concepts in Aristotle’s philosophy is typical of Alexander’s philosophical stance in general. He regards universals as inseparable from particulars and as secondary to them, and stresses the unity of matter and form. Similarly, he treats the human soul as the perishable form imposed upon the bodily elements to constitute a living human being. He argues that the intellect develops from an embodied intellect (that is focused upon the material world) to a state that eventually contains forms that are not embodied. He rules out personal immortality by identifying the active intellect with pure form and with God, the Unmoved Mover (see On the Soul and Caston 2012). In his emphasis on a naturalist point of view he appears remarkably free from the increasingly spiritualistic and mystical tendencies of his own time. In the treatise On Mixture and Increase Alexander expands on problems that Aristotle touched upon only briefly in On Generation and Corruption I 10, but his main concern is — as it is in his On Fate — to prove that the Stoic position of a ‘thorough’ mixture of two substances cannot be maintained. These treatises suggest that at the beginning of the third century philosophical discussions between the traditional schools were still lively. We have, of course, no other evidence on that issue. But there would be little point in proving the superiority of the Peripatetic doctrine, as he does in On Fate, to the emperors if the issue was by general consent regarded as obsolescent. It is unlikely, therefore, that Alexander’s polemics are only a kind of shadow-boxing against long-gone adversaries.