occasion arises for changing thoughts into images. But the analysis- and still more plainly the synthesis- of such dreams as show no regression towards images, e.g., the dream Autodidasker: Conversation with Professor N, reveals the same processes of displacement and condensation as do the rest.

We cannot, therefore, avoid the conclusion that two kinds of essentially different psychic processes participate in dream- formation; one forms perfectly correct and fitting dream- thoughts, equivalent to the results of normal thinking, while the other deals with these thoughts in a most astonishing and, as it seems, incorrect way. The latter process we have already set apart in chapter VI as the dream-work proper. What can we say now as to the derivation of this psychic process?

It would be impossible to answer this question here if we had not penetrated a considerable way into the psychology of the neuroses, and especially of hysteria. From this, however, we learn that the same "incorrect" psychic processes- as well as others not enumerated- control the production of hysterical symptoms. In hysteria, too, we find at first a series of perfectly correct and fitting thoughts, equivalent to our conscious ones, of whose existence in this form we can, however, learn nothing, i.e., which we can only subsequently reconstruct. If they have forced their way anywhere to perception, we discover from the analysis of the symptom formed that these normal thoughts have been subjected to abnormal treatment, and that by means of condensation and compromise-formation, through superficial associations which cover up contradictions, and eventually along the path of regression, they have been conveyed into the symptom. In view of the complete identity between the peculiarities of the dream-work and those of the psychic activity which issues in psychoneurotic symptoms, we shall feel justified in transferring to the dream the conclusions urged upon us by hysteria.

From the theory of hysteria we borrow the proposition that such an abnormal psychic elaboration of a normal train of thought takes place only when the latter has been used for the transference of an unconscious wish which dares from the infantile life and is in a state of repression. Complying with this proposition, we have built up the theory of the dream on the assumption that the actuating dream-wish invariably originates in the unconscious; which, as we have ourselves admitted, cannot be universally demonstrated, even though it cannot be refuted. But in order to enable us to say just what repression is, after employing this term so freely, we shall be obliged to make a further addition to our psychological scaffolding.

We had elaborated the fiction of a primitive psychic apparatus, the work of which is regulated by the effort to avoid accumulation of excitation, and as far as possible to maintain itself free from excitation. For this reason it was constructed after the plan of a reflex apparatus; motility, in the first place as the path to changes within the body, was the channel of discharge at its disposal. We then discussed the psychic results of experiences of gratification, and were able at this point to introduce a second assumption, namely, that the accumulation of excitation- by processes that do not concern us here- is felt as pain, and sets the apparatus in operation in order to bring about again a state of gratification, in which the diminution of excitation is perceived as pleasure. Such a current in the apparatus, issuing from pain and striving for pleasure, we call a wish. We have said that nothing but a wish is capable of setting the apparatus in motion and that the course of any excitation in the apparatus is regulated automatically by the perception of pleasure and pain. The first occurrence of wishing may well have taken the form of a hallucinatory cathexis of the memory of gratification. But this hallucination, unless it could be maintained to the point of exhaustion, proved incapable of bringing about a cessation of the need, and consequently of securing the pleasure connected with gratification.

Thus, there was required a second activity- in our terminology the activity of a second system- which would not allow the memory- cathexis to force its way to perception and thence to bind the psychic forces, but would lead the excitation emanating from the need-stimulus by a detour, which by means of voluntary motility would ultimately so change the outer world as to permit the real perception of the gratifying object. Thus far we have already elaborated the scheme of the psychic apparatus; these two systems are the germ of what we set up in the fully developed apparatus as the Ucs and Pcs.