smallest expenditure of innervation. Let us, however, keep to the fact — this is the key to the theory of repression — that the second system is capable of occupying an idea only when it is in position to check the development of pain emanating from it. Whatever withdraws itself from this inhibition also remains inaccessible for the second system and would soon be abandoned by virtue of the principle of pain. The inhibition of pain, however, need not be complete; it must be permitted to begin, as it indicates to the second system the nature of the memory and possibly its defective adaptation for the purpose sought by the mind.

The psychic process which is admitted by the first system only I shall now call the primary process; and the one resulting from the inhibition of the second system I shall call the secondary process.