De anima
"On the Soul" ("De anima") is a treatise on the soul written along the lines suggested by Aristotle in his own "De anima". Alexander contends that the undeveloped reason in man is material ("nous hylikos") and inseparable from the body. He argued strongly against the doctrine of the soul's immortality. He identified the active intellect ("nous poietikos"), through whose agency the potential intellect in man becomes actual, with God. A second book is known as the "Supplement to On the Soul" ("Mantissa"). The "Mantissa" is a series of twenty-five separate pieces of which the opening five deal directly with psychology. The remaining twenty pieces cover problems in physics and ethics, of which the largest group deals with questions of vision and light, and the final four with fate and providence. The "Mantissa" was probably not written by Alexander in its current form, but much of the actual material may be his.