The title of this chapter may seem paradoxical, pleasure being as a rule the expression of health, and even of exuberant life, and pain, by its very definition, a diseased state. It must be admitted that, for the latter, the expression _abnormal_ would be preferable. However, the facts we are about to study are not rare, and deserve separate examination, because the deviations and anomalies of pleasure and pain serve to make the nature of each better understood. Taking our subject, for the first time, on the pathological side, a proceeding to be applied later on to each of the simple or complex emotions in turn, certain preliminary remarks are indispensable. The application of the pathological method to psychology needs no justification; its efficacy has been proved. The results obtained are too numerous and too well known to need enumeration. This method, in fact, has two principal advantages—(1) it is a magnifying instrument, amplifying the normal phenomenon; hallucination explains the part played by the image, and hypnotic suggestion throws light on the suggestion met with in ordinary life; (2) it is a valuable instrument of analysis. Pathology, it has justly been remarked, is only physiology out of order, and nothing leads better to the understanding of a machine than the elimination or the deviation of one of its wheels. Aphasia produces a decomposition of memory and its different signs, which the subtlest psychological analysis could not attempt or even suspect. The principal difficulty of this method lies in determining the precise moment when it can be applied. The distinction between the healthy and the morbid is often extremely difficult to establish. No doubt there are cases where no hesitation is possible; but there are also debatable zones lying between the territories of health and disease. Claude Bernard ventured to write, “What is called the normal state is purely a conception of the mind, a typical ideal form entirely disengaged from the thousand divergences among which the organism is incessantly floating, amid its alternating and intermittent functions.” If this is the case with regard to bodily health, we may expect to find it still more so with regard to mental. The dilemma: Either this man is mad or he is not, is, in many cases, says Griesinger, meaningless. The psychical organism, being more complex and less stable than the physical, makes it still more difficult to fix a norm. Finally, this difficulty attains its maximum in our subject, because the emotional—the most mobile among all the forms of psychic life—oscillates incessantly around one point of equilibrium, always ready to sink too low or rise too high. As, however, it is necessary to adopt some definite characteristics which may serve as pathological signs, as criteria for distinguishing the healthy from the morbid in the emotional order, we shall accept those proposed by Féré. According to him, an emotion may be considered as morbid—