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A version published in: John Shannon Hendrix, Robert Grosseteste: Philosophy of Intellect and Vision, Sankt Augustin: Academia Verlag, 2010.


Themistius (317–c. 387) was born into an aristocratic family and ran a paripatetic school of philosophy in Constantinople in the mid-fourth century, between 345 and 355. He made use of Alexander’s De anima in his commentary on the De anima of Aristotle, which is considered to be the earliest surviving commentary on Aristotle’s work, as Alexander’s commentary itself did not survive. Themistius may also have been influenced by Plotinus, and Porphyry (232–309), whom he criticizes. Themistius refers often to works of Plato, especially the Timaeus, and attempts a synthesis of Aristotle and Plato, a synthesis which was continued in the Neoplatonic tradition. As it has been seen in Alexander that thought and perception are intimately connected, almost identical, Themistius goes to much greater length to differentiate the two. Sense perception must be distinguished from reasoning, because all animals are capable of sense perception, while only humans are capable of reasoning; while there are only five kinds of sense perception, there are many varieties of the capacity for reasoning; and the functions of sense perception and reasoning can be differentiated.