Dictionary of Greek and Roman Biography and Mythology/Theodosius (literary) 2.

THEODO′SIUS, 2. Of Tripolis, a mathematician and astronomer of some distinction, was a philosopher of the sect of the Sceptics, or, to speak more exactly, a follower of Pyrrhon, whose philosophy, Theodosius himself contended, ought not properly to be called sceptical (Diog. Laërt. ix. 70). Among other works of his, Suidas (s. v.) mentions a Commentary on the κεφάλαια of Theudas, who appears from another passage of Diogenes (ix. 116) to have lived not very long before the time of Sextus Empiricus, and therefore about the reign of Trajan. Suidas also enumerates σκεπτικὰ κεφάλαια among the works of Theodosius (s. v. and also s. v. Πυῤῥώνιος), and the same work is mentioned by Diogenes (ix. 70). Of the ancient mathematicians, Ptolemy does not refer to Theodosius, but his works are quoted by Theon, in his Commentary on Ptolemy, by Pappus, in his συναγωγή, and by Proclus, in his Hypotyposis Astronomica, p. 7.

Suidas mentions the following as his mathematical and astronomical works : -Σφαιρικὰ ἐν Βιβλίοις τρισίν, Περὶ ἡμερῶν καὶ νυκτῶν δύο, ὑπόμνημα εἰς τὸ Ἀρχιμήδους Ἐφόδιον, Διαγραφὰς οἰκιῶν ἐν Βιβλίοις γ, Ἀστρολογικά, Περὶ οἰκήσεων. Of these works, some have been printed.

The work on the Sphere, which is a treatise on the properties of the sphere, and of the circles described on its surface, was first published in an ancient Latin version, edited by John Vögelin, Paris, 1529, 4to.; and other Latin versions were published by F. Maurolycus, with the Sphaerica of Menelaus, and the work of Autolycus on the Sphere, Messanae, 1558, fol.; by Jos. Auria, with Autolycus, from six MSS. in the Vatican, 1588, 4to.; by Dr. Isaac Barrow, in his edition of Archimedes, Lond. 1675, 4to.; and by And. Celsius, Upsal. 1730, 12mo. The first edition of the Greek text was published by Joannes Pena, the royal mathematician of France, Bellov. 1558, 4to.: many of the demonstrations, which are defective in the work of Theodosius, were supplied by Pena from Euclid's Elements, and other geometrical works, both ancient and modern. Another edition, founded on that of Pena, with the further aid of some MSS. at Oxford, from which, however, no readings of consequence were obtained, was published by Joseph Hunt, Oxon. 1707. 8vo. There are also translations of the work into English, by Edward Sherbourne, as an appendix to his version of the Sphaerica of Manilius, Lond. 1675, fol., and into German, by E. Nizze, whose notes are of high value, Stralsund, 1826, 8vo.

His work περὶ ημερῶν καὶ νυκτῶν, de Diebus et Noctibus, was published from a MS. in the Vatican, in Latin only, with ancient Scholia, and figures, by Jos. Auria, Romae, 1591, 4to.; the propositions, without demonstrations, having been previously edited by Conrad Dasypodius, Argentorat. 1572, 8vo. Fabricius states that the book Περὶ οἰκήσεων was also published in Latin, by Jos. Auria, Romae, 1587, 4to.; but the edition is not mentioned in Hoffmann's Lexicon Bibliographicum. In the great collection of the works of the ancient mathematicians, planned by Edward Bernard, after whose death the synopsis of the intended edition was published by Thomas Smith, Lond. 1704, 8vo., the known works of Theodosius were to have had a place in the seventh volume. There are many MSS. of the above three works, in the principal libraries of Europe, in Greek, Latin, and Arabic. The other works of Theodosius appear to be entirely lost. (Fabric. Bibl. Graec. vol. iv. pp. 21 - 23, 213; Menag. ad Diog. Laërt. ix. 70.)