The most distinguished Syriac scholar of this later period was Severus Sebokht (d. 666-7), Bishop of Kennesrin. He wrote letters on theological subjects to Basil of Cyprus and Sergius, abbot of Skiggar, as well as two discourses on St. Gregory Nazianzen. On Aristotelian logic he composed a treatise on the syllogisms in the Analytics of Aristotle, a commentary on the Hermeneutics which was based on the commentary of Paul the Persian, a letter to Aitilaha of Mosul on certain terms used in the Hermeneutics (Brit. Mus. Add. 17156), and a letter to the periodeutes Yaunan on the logic of Aristotle (Camb. Univ. Lib. Add. 2812). In addition to these works on logic he also wrote on astronomical subjects (Brit. Mus. Add. 14538), and composed a treatise on the astronomical instrument known as the astrolabe, which has been edited and published by F. Nau (Paris, 1899). In all this he showed himself the product of Alexandrian science and illustrated the widening scientific interests of the period. It seems that he took steps towards introducing the Indian numerals, but this was not carried on by any immediate successor. His work represents the highest level reached by any Syriac scientist and this, it will be noted, was associated with Kennesrin.
In 662 he wrote concerning Arabic numerals:
- 'I will omit all discussion of the science of the Indians, ... , of their subtle discoveries in astronomy, discoveries that are more ingenious than those of the Greeks and the Babylonians, and of their valuable methods of calculation which surpass description. I wish only to say that this computation is done by means of nine signs. If those who believe, because they speak Greek, that they have arrived at the limits of science, would read the Indian texts, they would be convinced, even if a little late in the day, that there are others who know something of value.'
Severus Sebokht on Indian numerals: F. Nau, 'La plus ancienne mention orientale des chiffres indiens', Journal asiatique 10:16 (1910), 225-227.
On the Constellations: Ms. Paris Syr. 346, for which see F. Nau, in Revue de l’Orient Chrétien 27 (1929/30), 327-410, 28 (1932), 85-100.
On the astrolabe: English translation by M. Margoliouth, in R. Gunther, Astrolabes of the World. I, The Eastern Astrolabes (Oxford, 1932), 82-103.
Sebokht, Sévère, in françois Nau, « le Traité Sur l’astrolabe de Sévère Sebokht », JA, série 9, t. xiii, 1899, P. 238-303.