But, one may say, if pain and hurtful acts on the one hand, pleasure and serviceable acts on the other, form indissoluble pairs, of such a kind that the painful state in consciousness is the equivalent of destructive acts in the organism, and inversely, we should here have an interversion—pleasure would express disorganisation; pain, reorganisation. This hypothesis is not a very probable one, and scarcely seems necessary. If we admit, as has been said in the preceding chapter, that there always exist two simultaneous and opposite processes whose difference is all that is perceptible to the consciousness, it is sufficient for one of the processes to be accelerated or the other retarded, in an abnormal manner, in order to change the difference in favour of one or the other. No doubt the final result contradicts the rule, since in the above cases the surplus which ought to be negative (pain) is positive (pleasure). But this is a new proof that we are confronted with a deviation, an anomaly, a pathological case to be treated as such. I have taken by itself and studied a typical case; it now remains, not to enumerate, but to classify pathological pleasures in order to show their frequency. Taking as a guide the excellent definition of Mantegazza, “Morbid pleasure is that which is either the cause or the effect of an evil,” I divide them into three classes. 1. Semi-pathological pleasures, which form the transition from the healthy to the frankly morbid. These require an excessive or prolonged expenditure of vital energy. We know that the pleasures of taste, smell, sight, hearing, touch, muscular exercise, the sexual relations, produce fatigue and exhaustion, or even suddenly become painful. The pleasures of affection, of self-love, of possession, when they become passions—that is to say, when they increase in intensity and stability—cease to be pure pleasures; a painful element is added to them. This phenomenon is natural and logical, since every increase in activity entails losses, and consequently conditions of pain. This class is scarcely morbid, since pain here _succeeds_ pleasure. This is not the case with the other two, in which pleasure rises from the midst of destruction, and dominates the consciousness.