An interesting train of thought now presents itself if we consider the
relations of this inhibition of discharge by the second system to the
regulation through the principle of pain. Let us now seek the
counterpart of the primary feeling of gratification, namely, the
objective feeling of fear. A perceptive stimulus acts on the primitive
apparatus, becoming the source of a painful emotion. This will then be
followed by irregular motor manifestations until one of these withdraws
the apparatus from perception and at the same time from pain, but on the
reappearance of the perception this manifestation will immediately
repeat itself (perhaps as a movement of flight) until the perception has
again disappeared. But there will here remain no tendency again to
occupy the perception of the source of pain in the form of an
hallucination or in any other form. On the contrary, there will be a
tendency in the primary apparatus to abandon the painful memory picture
as soon as it is in any way awakened, as the overflow of its excitement
would surely produce (more precisely, begin to produce) pain. The
deviation from memory, which is but a repetition of the former flight
from perception, is facilitated also by the fact that, unlike
perception, memory does not possess sufficient quality to excite
consciousness and thereby to attract to itself new energy. This easy and
regularly occurring deviation of the psychic process from the former
painful memory presents to us the model and the first example of
_psychic repression_. As is generally known, much of this deviation from
the painful, much of the behavior of the ostrich, can be readily
demonstrated even in the normal psychic life of adults.

By virtue of the principle of pain the first system is therefore
altogether incapable of introducing anything unpleasant into the mental
associations. The system cannot do anything but wish. If this remained