the Zohar:

In my first year of teaching at a seminary college, I assigned the Zohar, from the Jewish Cabalistic teachings. None of my students could make any sense of this teaching. It was crystal clear to me, but untenable for the students. I never again put these teaching's to first year students. And as the adage go's, a person can spend an entire life studying the Zohar, and never know its truth. You never understand the spirit from the brain, only from the heart.