- G. J. Toomer
Theon of *Alexandria (1) (fl. 364 ce), mathematical commentator. Extant works are (1) a commentary on *Ptolemy (4)'s Almagest (the sections on bk. 11 and parts of other books are lost); (2) a large commentary on the Handy Tables of Ptolemy; (3) a small introduction to the Handy Tables. He also produced ‘editions’ (i.e. trivial reworkings) of (a) *Euclid (Elements, Data, and Optics); (b) Ptolemy's Handy Tables, which exist only in Theon's version. Theon was competent in mathematics, but completely unoriginal; his importance lies in his role in the preservation and transmission of older works. It was in his version that Ptolemy's astronomical tables were known to Islamic science, whence they passed to medieval Europe.