Boris Sidis,
The Foundations of Normal and Abnormal Psychology…
(1914
| notes)
“ If we apply this very simple rule of logic to the theory of "unconscious ideas," we at once realize the illegitimate character of such a hypothesis. An idea is essentially of a conscious nature. To speak, therefore, of unconscious ideas, is to introduce into psychology the self-contradictory impossible concept of unconscious conscious ideas. This is equivalent to the assumption of an unconscious consciousness. An unconscious idea is neither a vera causa nor a fact ultimately to be verified. The conception of an unconscious idea is like the conception of a round square. ”
