(Σφαῖρος), called, apparently from the country of his birth, Βοσποριανός by Diogenes Laertius (7.177), and Βορυσθενιτης by Plutarch (Plut. Cleom. 100.2), was a philosopher of the Stoic school. He studied first under Zeno of Citium. and afterwards under Cleanthes. He lived at Alexandria during the reigns of the first two Ptolemies, having gone there apparently at the invitation of Ptolemy Philadelphus. He also taught at Lacedaemon, and was believed to have had considerable influence in moulding the character of Cleomenes. (Plut. l.c.) He was in considerable repute among the Stoics for the accuracy of his definitions (Cic. Tusc. 4.24.53). Diogenes Laertius (l.c.) and Athenaeus (viii. p. 334. e.) tell a story of the dexterous manner in which, on one occasion, by the help of his subtle distinctions, he saved himself from the necessity of admitting that he had been deceived by a trick played upon him by king Ptolemy. He was, according to Diogenes Laertius, the author of the following works and treatises :-- 1. Περὶ κόσμου.2. Περὶ στοιχείων σπέρματος.3. Περὶ τὺχης.4. Περὶ ἐλαχίστων (on the atomic theory).5. Πρὸς τὰς ἀτόμους καὶ τὰ ἔδωλα.6. Περὶ αἰσθητηρίων.7. Περὶ Ἡρακλειτου έ δίατρίβῶν.8. Περὶ τῆς ἠθικῆς διατάξεως.9. Περὶ καθήκοντος.10. Περὶ ὁρμῆς.11. Περὶ παθῶν, in two books.12. Διατριβαί.13. Περὶ βασιλείας.14. Περὶ Λακωνικῆς πολιτείας.Athenaeus (iv. p. 141 b.) quotes from the third book of this work.15. Περὶ Λυκούργου καὶ Σωκράτους, in three books. It does not appear whether it is this work or the preceding which is quoted by Plutarch (Lyc. 5.)16. Περὶ νόμου.17. Περὶ μαντικῆς.18. Διάλογοι ἐρωτίκοί.19. Περὶ τῶν Ἐρετριακῶν φιλοσόφων.20. Περὶ ὁμοίων.21. Περὶ ὅρων.22. Περὶ ἕξεως.23. Περὶ τῶν ἀντιλεγομένων.24. Περὶ λόγου.25. Περὶ πλούτου.26. Περὶ δόξης.27. Περὶ θανάτου.28. Τέχνη διαλεκτική, in two books.29. Περὶ κατηγορημάτων.30. Περὶ ἀμφιβολιῶν.31. Epistles. None of these are now extant. Diogenes Laertius (7.178), mentions a treatise by Chrysippus against some of the views entertained by Sphaerus. (Fabric. Bibl. Gr. vol. iii. p. 576; Vossius, de Hist. Graec. p. 140; Schöll Gesch. der Griech. Litt. vol. ii. p. 216.)