he 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. I
show by another point for what purpose the second system is obliged to
correct the primary process. The primary process strives for a discharge
of the excitement in order to establish a _perception_ identity with the
sum of excitement thus gathered; the secondary process has abandoned
this intention and undertaken instead the task of bringing about a
_thought identity_. All thinking is only a circuitous path from the
memory of gratification taken as an end-presentation to the identical
occupation of the same memory, which is again to be attained on the
track of the motor experiences. The state of thinking must take an
interest in the connecting paths between the presentations without
allowing itself to be misled by their intensities. But it is obvious
that condensations and intermediate or compromise formations occurring
in the presentations impede the attainment of this end-identity; by
substituting one idea for the other they deviate from the path which
otherwise would have been continued from the original idea. Such
processes are therefore carefully avoided in the secondary thinking. Nor
is it difficult to understand that the principle of pain also impedes
the progress of the mental stream in its pursuit of the thought
identity, though, indeed, it offers to the mental stream the most
important points of departure. Hence the tendency of the thinking
process must be to free itself more and more from exclusive adjustment
by the principle of pain, and through the working of the mind to
restrict the affective development to that minimum which is necessary as
a signal. This refinement of the activity must have been attained
through a recent over-occupation of energy brought about by
consciousness. But we are aware that