I take shelter behind the inadequacy of the English language.
And now to the explanation of my use, or misuse, of the phrase.
It was not till I was a young man, at college, that I got any clew to the significance of my dreams, and to the cause of them.

Up to that time they had been meaningless and without apparent causation.

But at college I discovered evolution and psychology, and learned the explanation of various strange mental states and experiences.

For instance, there was the falling-through-space dream--the commonest dream experience, one practically known, by first-hand experience, to all men.
This, my professor told me, was a racial memory.

It dated back to our remote ancestors who lived in trees.