 As for logic, al-Farabi even exerted a stronger influence over Medieval Jewish philosophy, which was apparently almost like that exerted by the most highly reputed, “official” commentator of Aristotelian logic: Averroes. According to Maimonides, there was no need to study logical texts, apart from those by al-Farabi, since “all that he wrote… is full of wisdom, and… he was a very valid author” (Marx 1934–1935, 379). Surely, al-Farabi’s logical (and also non-logical) works influenced the Treatise On the Art of Logic (Maqala fi sina‘a al-mantiq) usually ascribed to Maimonides, and probably written around 1160 (see Brague 1996; Maimonides’ authorship has been recently challenged by Davidson 2005, 313–322): this text was thrice translated into Hebrew in the 13th and 14th centuries and was obviously widespread among Jewish readers in the Late Middle Ages. As a matter of fact, almost all his logical works were either translated into Hebrew, or at least widely employed by a number of Medieval Jewish philosophers in the 13th-15th centuries (among the others, by Samuel Ibn Tibbon in his Commentary on the Difficult Terms [Perush ha-millot ha-zarot]: Robinson 2009), although the real extent of his influence on Jewish logic has not yet been examined in all its aspects. As for the many Hebrew translations of his summaries or “short commentaries” on Porphyry’s Isagoge and Aristotle’s Organon, probably five groups of these translations (not covering the whole series of the summaries) can be identified: some translations were made very early, possibly before 1200; some others should be ascribed to a Spanish Jew, Moses Ibn Lagis; some others were made by members of the family of the Ibn Tibbons, during the 13th century, and were often employed as sources by some 14th- and 15th-centuries Jewish philosophers (Judah ben Isaac Cohen, Abraham Avigdor); other translations consisted in revisions of the Tibbonian ones, were made before 1320 and were surely known to Hezekiah bar Halafta (see below, 7); finally, two translations (the only ones of al-Farabi’s summaries of Aristotle’s Rhetoric and Poetics) were probably made by Todros Todrosi, a philosophical translator working in Arles, around 1330 (about all these translations, see Zonta 1996, 189–193). In particular, al-Farabi’s summary of the Categories was quoted and commented on by an otherwise unknown Jewish philosopher, Sar Shalom, possibly active in Provence around 1300 (Zonta 1997b, 523). Also some of al-Farabi’s “long commentaries” (tafasir) on Aristotle’s logic, even those now lost in their Arabic original text, can be shown to have influenced Jewish philosophers: the Long Commentary on Categories is preserved almost only due to the many quotations made by a Late Medieval Jewish author, Judah ben Isaac Cohen, and has very recently been published (Zonta 2006a); the Long Commentary on De interpretatione, found in Arabic, was translated into Hebrew before 1334 (the text of its introduction in Hebrew is still extant) and appears to have influenced Gersonides too (Glasner 2002, 252–254); many passages from the Long Commentary on Book Eight of Topics, lost in Arabic, were translated into Hebrew by Todros Todrosi in 1334. As proved by Georges Vajda (Vajda 1965), Maimonides knew and implicitely employed al-Farabi’s summary of Topics, book one, chapter 11, as a source of a passage of his Guide of the Perplexed, part two, chapter 25, concerning a discussion between the two different doctrines of the eternity of the world according to Aristotle and Plato; he also knew and paraphrased some passages from other logical works by al-Farabi (the summary of De interpretatione, the Long Commentary on Prior Analytics: see Davidson 2005, 113–114).