Perhaps the most imporant book on Jewish philosophy ever written in Maimonides’ Guide for the Perplexed (מורה נבוכים, Moreh Nevukhim.) Yet it is also one of the most misunderstood Jewish books.
Maimonides’s arguments can’t be followed at all, unless one is first familiar with the Hebrew Bible, and the relation of it to classical rabbinic literature (Mishnah, Midrash, Talmud.) Next, one must understand that all of his philosophy relates to Aristotle, and the contemporary neo-Aristotelian literature discussed by that era’s Jewish, Muslim and Christian scholars.
One doesn’t need to be an expert one’s self in all these philosophers, but one does need to know Maimonides brought these ideas into his own work (it is standard for philosophers to read each other’s works, and share and critique ideas.) In particular Maimonides references the ideas of:
Abu Bakr al-Razi (850-925 circa)
“As for Maimonides’ harsh judgement of al-Razi as a philosopher, it was clearly based upon the knowledge of the general contents of his metaphysics and theology as found in al-Razi’s Book of Divine Science as found both in his Guide of the Perplexed (Dalalat al-ha’irin) and in one of his letters to the “official” translator of his work, Samuel Ibn Tibbon. ”
al-Farabi, Abu Nasr (c.870-950)
“As for logic, al-Farabi even exerted a stronger influence over Medieval Jewish philosophy… 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.” 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”
“…According to Pines, although al-Farabi’s former work is not explicitely quoted in the Guide of the Perplexed, it was surely among the main sources of Maimonides’ doctrine about the different roles played by the philosopher and by the prophet. Al-Farabi’s idea about the relationship between philosophy and religion, according to which the former is in a substantially higher position with respect to the latter, as found in his Book on Letters (Kitab al-huruf) and Book on Religion (Kitab al-milla), strongly influenced Maimonides’ ideas about this; moreover, the Book on Letters was later employed as a source for Falaquera’s treatment of linguistics in his Beginning of Science. According to Davidson, Maimonides explicitly quoted and employed al-Farabi’s Political Regime under the title The Changing Beings (al-Mawjudat al-mutaghayyira) for discussing the question of the world’s eternity in part two, chapter 74, of the Guide”
Avicenna (real name: Ibn Sina, Abu ‘Ali al-Husayn) (980-1037)
“. Although clear echoes of Avicennian doctrines about the distinction between essence and existence, between necessary and contingent beings, as well as the well-known Avicennian proof of the existence of God, have been found in the Guide of the Perplexed (see Moses Maimonides 1962, 1:xciii-ciii), the explicit judgement of Maimonides about Avicenna’s thought appears to be substantially cool (for a different interpretation of this judgement, see however Dobbs-Weinstein 2002). In his letter to Samuel Ibn Tibbon, he affirms that “Avicenna’s books, although they are subtle and difficult, are not like those by al-Farabi; however, they are useful, and he too is an author whose words should be studied and understood”
Abu Bakr Ibn Bajja aka Ibn al-Sa’igh (d. 1138),
“…Maimonides had the highest esteem of Ibn Bajja: he affirmed that “he was a great and wise philosopher, and all his works are right and correct”, and possibly appreciated him as a commentator of Aristotle too (Marx 1934–1935, 379). In some cases he was surely influenced by Ibn Bajja’s thought: in the Guide of the Perplexed, he explicitly refers to some of his philosophical and scientific ideas”
The above is a short excerpt from the article “Influence of Arabic and Islamic Philosophy on Judaic Thought” in The Stanford Encyclopedia of Philosophy.