From “The Invention of Influence”

Freud could never be certain, he said, in view of   his wide and early reading, whether what seemed like a new creation might not be the work instead of   hidden channels of memory leading back to the notions of others absorbed, coming now anew into form he’d almost known within him was growing. He called it (the ghost of a) cryptomnesia. So we own and owe what we know.