R' Abbahu said: All the forty days that Moses was on high, he kept on forgetting the Torah he learnt. He then said: 'Lord of the Universe, I have spent forty days, yet I know nothing.' What did God do? At the end of the forty days, He gave him the Torah as a gift, for it says, AND HE GAVE UNTO MOSES. Could then Moses have learnt the whole Torah? Of the Torah it says: The measure thereof is longer than the earth, and broader than the sea (Job 11:9); could then Moses have learnt it all in forty days? No; but it was only the principles thereof which God taught Moses.
-Exodus Rabbah 41:6
This is an interesting midrash. The most striking point is that it says that God only taught Moshe the principles of the Torah - which runs contrary to the typical Orthodox perspective that God revealed all of the Torah and all of the Oral Law to him. But secondly, there's the point that "Torah" is defined here not as the Pentateuch, but through the reference in Job which uses "The measure..." to describe the mysteries and (non)limits of God - "Torah" is then defined essentially as all metaphysical truth of God's ways.
7 "Can you fathom the mysteries of God? Can you probe the limits of the Almighty?
8 They are higher than the heavens—what can you do? They are deeper than the depths of the grave—what can you know?
9 Their measure is longer than the earth and wider than the sea.
So what is the midrash saying that Moshe received at Sinai? He received the principles of metaphysical truth.
For those of a skeptical bent who yet still recognize wisdom in the scriptures, this may be a helpful perspective in one's approach to Judaism.