At some time around 200 A.D., the Stoic philosopher and teacher Cleomedes delivered a set of lectures on elementary astronomy as part of a complete introduction to Stoicism for his students. The result was "The Heavens" (Caelestia), the only work by a professional Stoic teacher to survive intact from the first two centuries A.D., and a rare example of the interaction between science and philosophy in late antiquity. This volume contains a clear and idiomatic English translation - the first ever - of "The Heavens", along with an informative introduction, detailed notes, and technical diagrams. This important work will now be accessible to specialists in both ancient philosophy and science and to readers interested in the history of astronomy and cosmology but with no knowledge of ancient Greek.

"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.

Themistius' treatment of "Books 5-8" of Aristotle's "Physics" shows this commentator's capacity to identify, isolate and discuss the core ideas in Aristotle's account of change, his theory of the continuum, and his doctrine of the unmoved mover. His paraphrase offered his ancient students, as they will now offer his modern readers, an opportunity to encounter central features of Aristotle's physical theory, synthesized and epitomized in a manner that has always marked Aristotelian exegesis but was raised to a new level by the innovative method of paraphrase pioneered by Themistius. Taking selective but telling account of the earlier Peripatetic tradition (notably Theophrastus and Alexander of Aphrodisias), this commentator creates a framework that can still be profitably used by Aristotlian scholars today.

"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.