I read an article by a professor in Israel who suggests that the revelation at Mt Sinai was actually a drug-induced hallucination. I thought it was a ridiculous proposition, but it did get me thinking. How do we know that it was indeed G-d who spoke to Moses and not some mind-altering mushroom?
I read that article too. I am not sure what that professor was smoking when he wrote it.
There are several ways to test whether a revelation is truly divine or just the product of human imagination. One of them is by examining the content of the message. G-d never tells you what you want to hear. When people make up their own revelations, the message they convey tends to be very convenient and comfortable. But if it is indeed G-d talking, He most probably will demand from you something you never would have asked from yourself.
Imagine Moses came down from the mountain and said, "Ok guys, here's the deal. G-d wants us to chill out. He thinks we are just fine as we are. Eat whatever you want, be loose in your relationships, and live a life that feeds your every whim and fancy. Don't fuss over petty things like being honest in your business dealings or being nice to strangers. As long as you are good deep down in your heart and are true to yourself that's fine. We are here to have fun, not stress over little moral scruples."
Had Moses brought us this message, we would be justified to suspect that G-d may not have said that. But Moses did not bring us a message of self-assurance and convenience. Rather, he came down from the mountain and said the following (not an exact quote):
"Ok guys, here's the deal. G-d created the world as an unfinished project. And we have to do the rest. We are not here to serve ourselves, we are here to serve a higher purpose. We are naturally selfish, and we have to become selfless. We are physical and hedonistic, and we must become soulful and sensitive. We need to care for the poor and down-trodden, we need to love our neighbours even when they annoy us. We need to practice acts of goodness even if we are not in the mood. We have a huge mission to achieve - to change the world by changing ourselves. There is no promise that things will be easy for us. But this is our mission. So get to work."
The demands that G-d makes of us in the Torah are steep. They challenge us to our very core. This fact alone, while not proving anything, certainly indicates that Moses received the Torah when He was high on the mountain, not on anything else.