Leo29. Of THESSALONICA, an eminent Byzantine philosopher and ecclesiastic of the ninth century. Of the time or place of his birth nothing is known. He was the kinsman of the iconoclast Joannes (or as his enemies called him, on account of his obnoxious sentiments, Jannes), who was of the illustrious family of the Morocharzamii or Morochardanii, tutor of the emperor Theophilus, and patriarch of Constantinople, from about A. D. 832 --842. (Theoph. Contin. 4.26, comp. c. 6; and Symeon Magister, De Michaele et Theodora, c. 2.) Leo was characterized by his devotion to learning: he studied grammar and poetry "while staying (διατρίβων) at Constantinople," an expression which seems to indicate that he was not a native of that city; and rhetoric, philosophy, and arithmetic, under Michael Psellus, in the island of Andros. He visited the monasteries in the adjacent parts of continental Greece, examining and using their libraries, and studying and meditating upon the volumes obtained from them, amid the solitude of the mountains. Having thus acquired a great store of knowledge, not only in the sciences above mentioned, but in geometry, astronomy, including astrology, and music, he again visited Constantinople, and imparted his intellectual stores to those who resorted to him for instruction. (Theophan. Continuat. 4.29; Cedrenus, Compendium, p. 547, &c., ed. Paris, vol. ii. p. 165, &c., ed. Bonn.) Neither his learning, however, nor his connexions sufficed to raise him from obscurity, until he became, by a remarkable accident, known to the emperor Theophilus. A pupil of Leo, whom he had instructed in geometry, accepted the office of secretary to a military officer, during the war between the emperor and the caliph Al-Mamoun; and, falling into the hands of the Moslems, or treacherously deserting to them, at the fall of Amorium (A. D. 839), became known to the caliph, who was a liberal patron of science. The young man, though he excited the admiration of the caliph and his court, by his geometrical attainments, professed himself to be " not a master, but only a learner," and so highly extolled the knowledge of Leo, that he was forthwith despatched to Constantinople, with a letter to him, inviting him to leave that city and resort to Bagdad. Fearful of being suspected of a treasonable correspondence with the enemy, Leo showed the letter to the logothete Theoctistus, by whom the matter was reported to the emperor. Leo was thus made known to Theophilus. The emperor first appointed him public teacher or professor, assigning him the church of the Forty Martyrs as a school, and soon after ordered the patriarch Joannes, who appears hitherto to have neglected his learned kinsman, to ordain him archbishop of Thessalonica (Theoph. Continuat. 4.27 ; comp. Symeon Magister, De Theophilo. c. 18-20; Georg. Monach. De Theophilo. c. 22, 23; Cedrenus, Compendium, l.c.; Zonar. 16.4). After three years, when Theophilus died (A. D. 342), and the government came into the hands of his widow Theodora, as the guardian of her son Michael, the iconoclastic party was overthrown, and Leo and Joannes were deposed from their sees: but Leo, whose worth appears to have secured respect, escaped the sufferings which fell to his kinsman's lot (Theoph. Cont. 4.9, 26; Sym. Mag. De Theoph. 20, De Michaele, c. 1) ; and when the Caesar Bardas, anxious for the revival of learning, established the Mathematical school at the palace of Magnaura, in Constantinople, Leo was placed at its head, with one, if not more of his former pupils for his fellow-teachers. (Theoph. Contin. 4.26; Cedrenus and Zonaras, ll. cc.) Leo was faithful to the interests of Bardas, whom he warned of the insidious designs of Basilius the Macedonian, afterwards emperor (Sym. Mag. De Michaele et Theodora, 40; Georg. Monach. De Mich. et Theodora, c. 25, 26). An anecdote recorded both by Symeon (De Basilio Maced. 5) and George (De Basil. Maced. c. 4), shews that Leo was living in A. D. 869 : how much later is not known. Symeon (De Mich. et Theodora, c. 46) has described a remarkable method of telegraphic communication, invented by Leo, and practised in the reigns of Theophilus and his son Michael. Fires kindled at certain hours of the day conveyed intelligence of hostile incursions, battles, conflagrations, and the other incidents of war, from the confines of Syria to Constantinople; the hour of kindling indicating the nature of the incident, according to an arranged plan, marked on the dial plate of a clock kept in the castle of Lulus, near Tarsus, and of a corresponding one in the palace at Constantinople.
Excerpta Varia Graecor. Sophistarum, has given (p. 398) Δέοντος τοῦ Φιλοσόφου Καρκῖνοι, Versus Carcini Leonis Philosophi, i. e. verses which may be read either backward or forward. They are probably the same which are in some MSS. or catalogues ascribed to Leo Grammaticus [see above, No. 15], but may be more probably ascribed to our Leo, among whose early studies poetry is mentioned.
Astrological WorksSeveral astrological collectanea extant in MS. in different European libraries, contain portions by Leo Philosophus, by which name the subject of the present article, who appears to have practised astrology (Theoph. Contin. 4.28, 5.14), is probably meant (Fabricius, Bibl. Graec. vol. iv. p. 148, Graec. De Marci Biblioth. p. 153; Catalog. Codd. MStorum Bibl. Regiae, Paris, fol. 1740, vol. ii. pp. 499, 500).
Μέθοδος προγνωστική, Methodus Prognostica or instructions for divining by the Gospel or the Psalter, by Leo Sapiens, in the Medicean library at Florence ( Bandini, Catalog. Codd. Laur. Medic. vol. iii. p. 339), is perhaps by another Leo.
Χρησμοί, Oracula, which are commonly ascribed to the emperor Leo VI. Sapiens, or the wise, and have been repeatedly published. But Leo of Thessalonica is generally designated in the Byzantine writers the philosopher (Φιλόσοφος), not the wise (σόφος), and if the published Oracula are a part of the series mentioned by Zonaras (15.21), they must be older than either the emperor or Leo of Thessalonica.