EBN SAHLĀN SĀVAJĪ, Qāżī ZAYN-AL-DĪN ʿOMAR (b. Sāva, fl. early 12th century), Persian philosopher and logician. After serving as a judge in his native city, he became disillusioned with public life and moved to Nīšāpūr, where he had more contact with other scholars. He earned his living by copying philosophical texts. He was often cited in the later Persian philosophical tradition, though he has remained almost unknown to Western historians of philosophy and logic. His works on logic, in which he made innovative proposals for the use of Persian in place of Arabic terms, were especially influential. Ebn Sahlān was among the few Islamic philosophers who questioned Aristotelian method, proposing revisions in the order of the subject matter in Organon. Thirteen books have been attributed to him, of which five have been published, three exist in manuscript, and the remainder are unknown or obvious misattributions. His al-Baṣāʾer al-naṣīrīyafi’l-manṭeq (ed. M. ʿAbdoh, Cairo, 1316/1899) has been used as a textbook on advanced logic at al-Azhar in Cairo for many years (Mowaḥḥed, p. 727; for details of his life, see Bayhaqī, p. 137; Šahrazūrī, 1396/1976, pp. 56-57; Kašf al-ẓonūn, ed. Yaltakaya and Bilge, I, p. 217).

Ebn Sahlān’s pioneering work on logic and the foundations of mathematics influenced Šehāb-al-Dīn Yaḥyā Sohravardī, founder of the illuminationist school of Islamic philosophy. Sohravardī followed his examination of “one,” its typology, its orders, the problems of defining it, and so on (Šahrazūrī, 1372 Š./1993, pars. 106 ff.; Ziai, chap. 2). In Sohravardī’s work there are many proposals for technical innovations in formal logic that seem to be based on Ebn Sahlān’s work: reduction of terms; formal redefinition of the second and third figures in the syllogism as simple inferences or reductions based on the first figure; critical reevaluation of negation in simple and compound propositions; and a number of other equivalence relations. Ebn Sahlān’s most obvious impact was on the restructuring of logic; he opposed the Peripatetics and the authority of Aristotle’s Organon, on one hand, and Islamic theologians, on the other; again his influence can be seen in Sohravardī’s Ḥekmat al-ešrāq (Šahrazūrī, 1372 Š./1993), where the subjects covered in the traditional nine books of the Arabic Organon are rearranged in two divisions: semantics and formal logic (goft-e rowšan konanda) in the first and proof theory, including material logic (ḥojaj), in the second.


Bibliography: (For cited works not given detail, see “Short References.”)

Abu’l-Ḥasan ʿAlī b. Zayd Bayhaqī, Tatemmat ṣewān al-ḥekmat, ed. M. Šafīʿ, Lahore, 1935.

Brockelmann, GAL, S. I, pp. 831-32.

M.-T. Dānešpažūh, ed., Moḵtaṣar fī ḏekr al-ḥokamāʾ al-yūnānīyīn wa’l-mellīyīn, FIZ 7, 1338 Š./1959, p. 321.

Ebn Sahlān Sāvajī, Tabṣera wa do resāla-ye dīgar dar manṭeq, ed. M.-T. Dānešpažūh, Tehran, 1337 Š./1958 (including biographical accounts).

Ṣ Mowaḥḥed, “Ebn-e Sahlān,” in DMBE III, pp. 726-28. Ṣafā, Adabīyāt III, p. 296.

Šams-al-Dīn Moḥammad b. Maḥmūd Šahrazūrī, Nozhat al-arwāḥ II, Hyderabad, 1396/1976.

Idem, Šarḥ-e ḥekmat al-ešrāq, ed. Ḥ. Żīāʾī (Ziai), Tehran, 1372 Š./1993.

H. Ziai, Knowledge and Illumination, Atlanta, 1990.

(Hossein Ziai)

Originally Published: December 15, 1997

Last Updated: December 6, 2011

This article is available in print.
Vol. VIII, Fasc. 1, p. 52-53