problem of squaring the circle. In April 2007, it was reported that imaging analysis had discovered an early commentary on Aristotle's Categories in the Archimedes Palimpsest, and Robert Sharples suggested Alexander as the most likely author. Original treatises There are also several extant original writings by Alexander. These include: On the Soul, Problems and Solutions, Ethical Problems, On Fate, and On Mixture and Growth. Three works attributed to him are considered spurious: Medical Questions, Physical Problems, and On Fevers. Additional works by Alexander are preserved in Arabic translation, these include: On the Principles of the Universe, On Providence, and Against Galen on Motion. 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. Problems and Solutions (Quaestiones) consists of three books which, although termed "problems and solutions of physical questions," treat of subjects which are not all physical, and are not all problems. Among the sixty-nine items in these three books, twenty-four deal with physics, seventeen with psychology, eleven with logic and metaphysics, and six with questions of fate and providence. It is unlikely that Alexander wrote all of the Quaestiones, some may be Alexander's own explanations, while others may be exercises by his students. Ethical Problems was traditionally counted as the fourth book of the Quaestiones. The work is a discussion of ethical issues based on Aristotle, and contains responses to questions and problems deriving from Alexander's school. It is likely that the work was not written by Alexander himself, but rather by his pupils on the basis of debates involving Alexander. On Fate is a treatise in