Sigmund Freud,
Dream Psychology — Chapter 8. The Primary and Secondary Process-Regression
(1920)
“ The system cannot do anything but wish. If this remained so the mental activity of the second system, which should have at its disposal all the memories stored up by experiences, would be hindered. But two ways are now opened: the work of the second system either frees itself completely from the principle of pain and continues its course, paying no heed to the painful reminiscence, or it contrives to occupy the painful memory in such a manner as to preclude the liberation of pain. ”
