The facts that have led us to believe in the supremacy of the pleasure-principle in psychic life also find expression in the hypothesis that there is an attempt on the part of the psychic apparatus to keep the quantity of excitation present as low as possible, or at least constant. This is the same supposition only put into another form, for, if the psychic apparatus operates in the direction of keeping down the quantity of excitation, all that tends to increase it must be felt to be contrary to function, that is to say painful. The pleasure-principle is deduced from the principle of constancy; in reality the principle of constancy was inferred from the facts that necessitated our assumption of the pleasure-principle. On more detailed discussion we shall find further that this tendency on the part of the psychic apparatus postulated by us may be classified as a special case of Fechner’s principle of the _tendency towards stability_ to which he has related the pleasure-pain feelings. In that event, however, it must be affirmed that it is not strictly correct to speak of a supremacy of the pleasure-principle over the course of psychic processes. If such existed, then the vast majority of our psychic processes would necessarily be accompanied by pleasure or would conduce to it, while the most ordinary experience emphatically contradicts any such conclusion. One can only say that a strong tendency towards the pleasure-principle exists in the psyche, to which, however, certain other forces or conditions are opposed, so that the ultimate issue cannot always be in accordance with the pleasure-tendency. Compare the comment of Fechner in a similar connection.[1] ‘Therewithal it is to be noted that the tendency towards the goal does not imply the attainment of it and that in general the goal is only approximately attainable....’ If we now address ourselves to the question of what circumstances have the power to frustrate the successful carrying out of the pleasure-principle we shall be treading on safer and better-known ground, and we can draw in abundant measure on our analytical experiences for the answer.