> There is an essay on the web that compares Freud's theory of the
> Unconscious to Schopenhauer's conception of the Will. I would be
> curious as to what you think about it.
Freud wrote explicitely that he used Schopenhauer for confirmation.
Freud only concentrated on a few aspects of the nonconscious, though,
and had to be supplemented later by Adler, Reich, Jung, and Rank.
Of courtse already before Freud there were Mesmer and Janet who
used a model of nonconscious mind, explaining techniques like
hypnosis for exploration.