Themistius ran his own philosophical school in Constantinople in the middle of the fourth century A.D. His paraphrases of Aristotle's writings are unlike the elaborate commentaries produced by Alexander of Aphrodisias, or the later Neoplatonists Simplicius and Philoponus. His aim was to provide a clear and independent restatement of Aristotle's text which would be accessible as an elementary exegesis.

But he also discusses important philosophical problems, reports and disagrees with other commentaries including the lost commentary of Porphyry, and offers interpretations of Plato.

Themistius' paraphrase of Aristotle's On the Soul is his most important and influential work. It is also the first extant commentary on this work of Aristotle to survive from antiquity. A rival to that of Alexander of Aphrodisias, it represents one of the main interpretations of Aristotle's theory of the intellect, which was debated throughout the Middle Ages and the Renaissance. It continues to be an important text for the reconstruction of Aristotle's philosophical psychology today.