Physician and man of letters, Ibn Kammuna left a number of writings on philosophy and religion. His treatise comparing Judaism, Christianity and Islam caused major rioting in Baghdad, forcing him to flee that city in secret. His commentary on al-Suhrawardi's Talwihat, the major text of Islamic Illuminationist philosophy remains one of the clearest and most thorough expositions of that branch of thought.
Of the major writings of 'Izz al-Dawla Sa'd bin Mansur ibn Kammuna, only the two that compare the views of religious communities have been published thus far. The longer one, the Tanqih al-abhath fi akhbar al-milal al-thalath (An Overview of Investigations into the Views of the Three Faiths) is sui generis in medieval literature. It begins with a extended investigation of prophecy, aiming to establish in a manner acceptable to adherents of all faiths (not just the prophetic ones) that revelation does occur. Here as elsewhere, Ibn Kammuna combines ideas culled from highly diverse sources including Moses Maimonides, Judah Halevi, al-Ghazali and Fakhr al-Din al-Razi. The next next three sections examine the most important prophetic traditions: Judaism, Christianity and Islam. Each section opens with an exposition of the basic tenets of the faith concerning its revealed Scripture, followed by a series of queries or objections, and the answers that a defender of that faith may be expected to give.
The presentation is dispassionate and eschews any polemical tone. Ibn Kammuna perhaps hoped that philosophical commitments shared by readers from the different faiths, and the unique political situation - the rulers were pagan Mongols bearing allegiance to none of the three faiths - would allow a calm examination of the scriptures sacred to each. The rioting against his book was perhaps incited by religious leaders, but it is not hard to understand why both Christians and Muslims were moved to write refutations of the book. It gives considerably more space to criticism of the sacred scriptures of the two 'daughter religions' than to the Torah, and it dwells on sectarian and other internal differences in Christianity and Islam but not in Judaism - although elsewhere Ibn Kammuna wrote an entire treatise on the differences between Rabbanites and Karaites.
It is not clear whether Ibn Kammuna attempted to formulate positions reflecting an actual consensus within each community (which would lend even greater historical interest to his text), or whether he forged his own synthesis from a melange of doctrines taken from existing literature. His fusion of the Halevi's chronicle of divine revelation from Adam onwards with Maimonides' rationalistic explanation of the ancient Israelite temple cult is not attested from other sources. It suggests that the book displays an original concatenation rather than an empirical study of views then normative in the three communities.
The treatise on the two major trends within Judaism in his day is considerably shorter. It devotes about twice as much space to Rabbanite views as to the Karaites, leading Leon Nemoy to conclude that, 'dispassionate critic though he was, his sympathies nevertheless remained with the mother synagogue' (Nemoy 1968: 109).
Ibn Kammuna's commentary on Ibn Sina's al-Isharat wa 'l-tanbihat is essentially a paraphrase, reflecting in a few places a somewhat different structure than the published text of Ibn Sina. Among its distinctive features are its division of the sciences, particularly the characterization of mathematical sciences as 'proto-physical' (ma qabla al-tabiy'a), balancing the accepted term for metaphysics, as 'what comes after the physics'. Ibn Kammuna offers his own interpretation of the story of Ibn Sina's Salman and Absal (the former symbolizes the rational soul, the latter the speculative intellect) and offers other unusual insights into the gnosis which Ibn Sina sketches in the third part of the book.
Ibn Kammuna's commentary on al-Suhrawardi's Talwihat is his longest work and, to judge from the number of surviving manuscripts, his most widely read. It seems to have played no small role in the development the 'illuminationist' (ishraqi) school of philosophy. Corbin noted the value of its exposition as well as its critical importance for establishing the text of the Talwihat. Nonetheless, about all that is available in print of this work are some brief quotations in Corbin's study and translations of selected passages by Shlomo Pines in footnotes to his studies of Abu 'l Barakat al-Baghdadi. The commentary is encyclopaedic, its discussions much fuller than those in the commentary on Avicenna. It promises to be a rich source for the exposition of Ishraqi philosophy and for a broad range of topics debated by thinkers of the period. The legitimacy of the so-called fourth figure of the syllogism, the possibility of alchemical transmutation of metals, and the nature of time are among the topics on which Ibn Kammuna offers lengthy disquisitions.
We know from manuscript catalogues that Ibn Kammuna wrote a number of other treatises in addition to those discussed above, but the only one published thus far is a short work on the immortality of the soul, a typically thorough survey. His impact on Jewish thought was minimal at best. Only his treatises on comparative religion and al-Suhrawardi were transcribed into Hebrew characters, none was widely diffused, and no citations of his writings have been found in the work of any other Jewish thinker. His works seem to have addressed the general, rather than the Jewish, public; the most influential of them, as noted, being his commentary on al-Suhrawardi.
See also: Illuminationist philosophy; al-SuhrawardiY. TZVI LANGERMANN