Experience tells us nothing about this. There have been some small traces of influences of this kind, but of such slight intensity that they cannot be compared with the intensity of the former homo-sexual component. On the conception that has been outlined, it is also incomprehensible how this homo-sexual component, regarded as so firmly fixed, can ever disappear without leaving active traces. To explain things, the process of development is called in, forgetting that this is only a word and explains nothing. You see, therefore, the urgent necessity of an adequate explanation of such a change of scene. For this we must have a dynamic hypothesis. Such commutations are only conceivable as dynamic or energic processes. I cannot conceive how manifestations of functions can disappear if I do not accept a change in the relation of one force to another. Freud’s theory did have regard to this necessity in the conception of components. The presumption of isolated functions existing side by side began to be somewhat weakened, more in practice than theoretically. It was replaced by an energic conception. The term chosen for this conception is “libido.” Footnote 4: No. 7 of this Monograph Series. CHAPTER III The Conception of Libido Freud had already introduced the idea of libido in his[5] “Three Contributions to the Sexual Theory” in the following words: “In biology, the fact that both mankind and animals have a sexual want is expressed by the conception of the sexual desire. This is done by analogy with the want of nourishment, so-called hunger. Popular speech has no corresponding characterization for the word ‘hunger,’ and so science uses the word ‘libido.’” In Freud’s definition, the term “libido” appears as exclusively a sexual desire. “Libido” as a medical term is certainly used for sexual desire, and especially for sexual lust. But the classical definition of this word as found in Cicero, Sallust, and others, was not so exclusive. The word is there used in a more general sense for every passionate desire. I only just mention this definition here, as further on it plays an important part in our considerations, and as it is important to know that the term “libido” has really a much wider meaning than is associated with it through medical language.