Now, for Freud, it is of just such cast off complexes, each with its own complement of energy, that the lowest level of the unconscious is made up. All the unethical acts and unsocial ways of thought of the child, repugnant to us to-day, still exist in the lowest dark chamber of the soul, not strong enough to break out into action, but alive. It is the penalty which we pay for our civilization, that it imposes standards of thought and action which are foreign to the deepest tendencies in us, modes of life of the cave-man and the ages before civilization, which have left their marks on the soul forever. And for all of us there has been some strain in adjusting to its requirements, resulting in the abandonment after a struggle of the old racial ways, and the substitution of newer and more ethical modes of action. But a part of our personality still remains in the troglodytic stage. We may not allow this part expression; we may not even be conscious that it longer exists, and yet it lives and works below the threshold, just as the remembrance of the death of her mother still affected the girl, though consciously it had lapsed. With the split between childhood and adolescence, the chasm between the old and the new becomes still wider; we turn our back more and more on the old ways; they lapse from consciousness more and more completely. Childhood seems a little alien to all of us; there has been a "transvaluation of all values" so that the remembrance of how we thought and felt then comes to us with the mark of a little strangeness upon it. It is strange just because we have cast it all out, we have "put away childish things." But in the dark limbo of the unconscious they still live on, unconscious though we may be that such is the case. The lowest level of the unconscious is thus far removed from consciousness in its modes of functioning. The conception that such tendencies still function, still need contiuual, though not conscious repression, is the essential point here.
But now what is the mechanism that prevents us from knowing that these old tendencies are still striving upward toward conscious expression? Consciousness is guarded from a knowledge of their existence and their activities, holds Freud, by the interposition of the upper level of the unconscious. This acts like a censor, a guard at the gate, and will not admit to conscious expression these outworn complexes, because of the pain which they would cause us if we were compelled to take account of them in our thinking. It would require too much energy consciously to keep them down; so it is the function of the upper level of the unconscious to save consciousness all this trouble, and to leave it free for other things. This it does, in ordinary circumstances, so well that we are not even aware that any repression is going on, or, indeed, that there is anything to repress. We have repressed our old complexes so long and so well that the act of repression has dropped below the conscious level; we are not aware of its existence. But, on