Jerusalem and Athens

It remains far beyond me to detail the avenues by which Platonic and Aristotelian ideas came to influence Judaism. However, it seems that the Greek conception of transcendence (e.g., the Absolute) along with the general rigor of Greek reasoning drove Jewish thinkers to envision a God that was ever more static and remote. The great medieval thinkers who wrote on this topic are well known, especially Rambam, Ralbag, and Crescas. But a millennium before Moreh Nevuchim was written, one of Judaism's most neglected philosophers and mystics gave us a surprisingly modern exposition of God's transcendence. Philo, "the first theologian," introduces the Jewish conception of unknowability (matt_90) with a Platonic expansion on the famous Exodus 33 conversation between God and Moses:

[Moses says] "But what Thou art in Thy essence I desire to understand, yet find in no part of the All any to guide me to this knowledge." [...] [God] replies, "Thy zeal I approve as praiseworthy, but the request cannot fitly be granted to any that are brought into being by creation. I freely bestow what is in accordance with the recipient; for not all that I can give with ease is within man's power to take, and therefore to him that is worthy of My grace I extend all the boons which he is capable of receiving. But the apprehension of Me is something more than human nature, yea even the whole heaven and universe will be able to contain. [...] But while in their essence they [God's powers] are beyond your apprehension, they nevertheless present to your sight a sort of impress and copy of their active working. You men have for your use seals which when brought into contact with wax or similar material stamp on them any number of impressions while they themselves are not docked in any part thereby but remain as they were. Such you must conceive My powers to be, supplying quality and shape to things which lack either and yet changing or lessening nothing of their eternal nature. Some of you call them not inaptly 'forms' or 'ideas,' since they bring form into everything that is, giving order to the disordered, limit to the unlimited, bounds to the unbounded, shape to the shapeless, and in general changing the worse to something better. Do not, then, hope to be ever able to apprehend Me or any of My powers in Our essence."

Further, Philo warns us that

To be anxious to continue his course yet further, and inquire about essence or quality in God, is a folly fit for the world's childhood. Not even to Moses, the all-wise, did God accord this, albeit he had made countless requests, but a divine communication was issued to him, "Thou shalt behold that which is behind Me, but My face thou shalt not see." This meant, that all that follows in the wake of God is within the good man's apprehension, while He Himself alone is beyond it, beyond, that is, in the line of straight and direct approach, a mode of approach by which (had it been possible) His quality would have been made known; but brought within ken by the powers that follow and attend Him; for those make evident not His essence but His subsistence from the things which he accomplishes.

While in Philo's view it certainly seems that aspects of God are unknowable by the human mind, he, like Maimonides later, does not take this as a cause for despair and disenchantment. Rather, Philo regards the recognition of God's unknowability as the highest goal of human inquiry:

When therefore the God-loving soul probes the question of the essence of the Existent Being, he enters on a quest of that which is beyond matter and beyond sight. And out of this quest there accrues to him a vast boon, namely to apprehend that the God or real Being is apprehensible by no one, and to see precisely this, that He is incapable of being seen.

Thus, in some sense, it is the recognition of the limits of human knowledge that itself represents the highest form of human knowledge, a sentiment echoed 1800 years later in R'Nachman's dictum that "The end of knowledge is [the realization] that we do not know" (green_92). Perhaps all mystics think alike, after all.

Next, the mystical approach...