[If so,] what did Moses, our teacher, want to comprehend when he requested: "Please show me Your glory" [Exodus 33:18]?
He asked to know the truth of the existence of the Holy One, blessed be He, to the extent that it could be internalized within his mind, as one knows a particular person whose face he saw and whose image has been engraved within one's heart. Thus, this person's [identity] is distinguished within one's mind from [that of] other men. Similarly, Moses, our teacher, asked that the existence of the Holy One, blessed be He, be distinguished in his mind from the existence of other entities, to the extent that he would know the truth of His existence as it is [in its own right].
He, blessed be He, replied to him that it is not within the potential of a living man, [a creature of] body and soul, to comprehend this matter in its entirety. [Nevertheless,] He, blessed be He, revealed to [Moses] matters which no other man had known before him - nor would ever know afterward - until he was able to comprehend [enough] from the truth of His existence, for the Holy One, blessed be He, to be distinguished in his mind from other entities, as a person is distinguished from other men when one sees his back and knows the structure of his body and [the manner in which] he is clothed.
This is alluded to by the verse [Exodus 33:23]: "You shall see My back, but you shall not see My face."