Life Theon of Smyrna (Θέων ὁ Σμυρναῖος) was a Platonist philosopher and mathematician active during the reign of Emperor Hadrian (117–138 CE) [1][2]. He is distinguished from the later Theon of Alexandria by his association with the city of Smyrna. Beyond this floruit and his philosophical orientation, no biographical details are recorded [1][2].

Works His only surviving work is the treatise Mathematics Useful for Understanding Plato (Τὰ κατὰ τὸ μαθηματικὸν χρήσιμα εἰς τὴν Πλάτωνος ἀνάγνωσιν), a compendium of arithmetic, geometry, harmonics, and astronomy intended as background for reading Plato’s Timaeus [1][2][3]. Two other works are attributed to him—On the Order of Plato's Writings and On Mathematical Signs—but these are considered spurious and do not survive [1].

Significance Theon’s surviving treatise is a valuable source for the state of mathematical astronomy in early Imperial Platonism. It systematically compiles earlier Pythagorean and astronomical knowledge, notably preserving summaries of planetary theories and the work of Adrastus of Aphrodisias [1][2][3]. The work illustrates the mathematical curriculum used to approach Platonic cosmology.

Sources 1. Stanford Encyclopedia of Philosophy (Theon of Smyrna): https://plato.stanford.edu/entries/theon-smyrna/ 2. Internet Encyclopedia of Philosophy (Theon of Smyrna): https://iep.utm.edu/theon-of-smyrna/ 3. Encyclopædia Britannica (Theon of Smyrna): https://www.britannica.com/biography/Theon-of-Smyrna