THEON of Smyrna
The date of " Theon of Smyrna the philosopher," to quote in full the account which Suidas gives of him, depends upon the assumption (which there seems no reason to dispute) that he is the Theon whom Ptolemy and the younger Theon mention as having made astronomical observations in the time of Hadrian. Theon of Smyrna certainly wrote on astronomy. On the assumption just made, Ptolemy has preserved his observations of Mercury and Venus (A. D. 129-133). Bouillaud supposes that it is Theon of Smyrna to whom Proclus alludes as having written on the genealogies of Solon and Plato, and Plutarch as having written on the lunar spots. (See Bouillaud's preface, or the quotations in Fabric. Bibl. Graec.
vol. iv. p. 35.)
All that we have left is a portion of a work entitled, Τῶν κατὰ μαθηματικὴν χρησίμων εἰς τὴν τοῦ Πλάτωνος ἀνάγνωσιν
The portion which now exists is in two books, one on arithmetic, and one on music : there was a third on astronomy, and a fourth περὶ τῆς ἐν κόσμῳ ἁρμονίας
The work on arithmetic is of the same character as that of NICOMACHUS; and as both these writers name Thrasyllus, and neither names the other, it may be supposed that the two were nearly contemporary.
The book on music is on the simplest application of arithmetic.
The two books were published by Bouillaud, from a manuscript in De Thou's library, Paris, 1644, quarto (Gr. Lat.). The book on arithmetic has been recently published, with Bouillaud's Latin, various readings, and new notes, by Professor J. J. de Gelder, Leyden. 1827, 8vo
: the preface is the fullest disquisition on Theon which exists. We may refer to it for an account of the bust which was found in Smyrna by Fouquier, with the inscription ΘΕΩΝΑΠΛΑΤΩΝ ΙΚΟΝΦΙΛΟΞΟΦΟΝΟΙΕΡΕΥΞΘΕΩΝΤΟΝΠΑΤΕΡΑ
, now in the museum at Rome.
There are scattered notices (for which see De Gelder) by which it seems that Theon had written other works : a manuscript headed θεολογούμενα
is mentioned as attributed to him, which is probably only the work known under that name, with an assumed authorship. Bouillaud mentions an astronomical fragment which he found; and also the assertion of Isaac Vossius, made to him, that an astronomical treatise existed in the Ambrosian library at Milan.