"On the Soul" was the most widely read of all the Aristotle commentaries in the Renaissance. The best-known of Themistius's discussions is that concerned with Aristotle's active intellect, which leads to his wider musings on the nature of the self. The 15,000 pages of the ancient Greek commentators on Aristotle, written mainly between 200 and 500 AD, constitute the largest corpus of extant Greek philosophical writing not translated into English or other European languages. This new series of translations, planned in 60 volumes, fills an important gap in the history of European thought.

"Physics Book 4" is one of Aristotle's most interesting works, discussing place, time and vacuum. Themistius was a fourth-century AD orator and essayist, not only a philosopher, and he thought that only paraphrases of Aristotle were needed, because there were already such comprehensive commentaries. Nonetheless, his paraphrastic commentaries are full of innovative comment. According to Aristotle, there is no such thing as 3-dimensional space. A thing's exactly-fitting place is a surface, the inner surface of its immediate surroundings. One problem that this created was that the outermost stars, on Aristotle's view, have no surroundings, and so no place. Themistius suggests that we might think instead of the neighbouring bodies which they surround as providing their place. Aristotle time as something countable, and concluded that it depends for its existence on that of conscious beings to do the counting. Themistius is in the minority among commentators in disagreeing. Themistius concurs with Aristotle in denying the existence of vacuum. We cannot think that a space formerly empty of body penetrates right through a body inserted into it. If one extension could penetrate another, says Themistius, a body could penetrate a body, because bodies occupy places solely in virtue of being extended.

Themistius' treatment of Books 1-3 of Aristotle's Physics presents central features of Aristotle's thought about principles, causation, change and infinity. The tradition of synthesising and epitomising exegesis is here raised to a new level by the innovative method of paraphrase pioneered by Themistius. Taking a selective, but telling, account of the earlier Peripatetic and Presocratic tradition, Themistius creates a framework that can still be profitably used in the study of Aristotle. This volume contains the first English translation of Themistius' commentary, accompanied by a detailed introduction, extensive explanatory notes and a bibliography.