The superior and truly human forms of emotion are reducible to four principal groups: the religious, moral, æsthetic, and intellectual sentiments. Although the somatic characters accompanying each of these will be noted with the greatest care in the second part of this work, it will be necessary, even at present, to enumerate the principal in advance. We must more especially be on our guard against the common error which insists in seeking emotion where nothing remains of it save a mere survival and shadow. If, _e.g._, we take the most intellectualised forms of the religious or the æsthetic sentiment, we shall have much trouble in recovering the physiological conditions of its existence. There is nothing surprising in this, all we have in this case being an abstract or extract of emotion, a simple mark, an emotional scheme, an affective substitute equivalent to those intellectual substitutes which take the place of the concrete. What we must study is true emotion, felt and expressed, not inadequately recalled to memory, a pale remnant of what once was an emotion. 1. The religious sentiment is attached—perhaps more than any other—to physiological conditions, because closely connected with the instinct of self-preservation, with the saving of the soul, under whatever form the believer may conceive it. The _intensity_ of the emotion alone is what concerns us; its quality is a matter for critical appreciation. We take the observable fact in the rough, whether legitimate or not. Now, does not the believer, whatever his degree of culture, whatever his religion, at the moment when he feels the emotion, tremble, turn pale, exhibit the _sacer horror_, the overwhelming awe which may end in unconsciousness, the prostrate attitude? Have not the mystics over and over again described the violent disturbances which agitate them, the internal tempest which ravages them, till, calm being re-established, they express themselves in language frequently recalling that of sexual love? The designation “hysterical,” bestowed, rightly or wrongly, on many of them, is based on the physical symptoms described by themselves. And have not the methods employed to excite, revive, or strengthen religious emotion, from the wine of the ancient Bacchanals to the noisy concerts of the Salvation Army, a direct physiological influence on the organs? What of the action of the rites which are only the fixed expression of a particular form of belief? and the miracles which happen in all religions to those who have “the faith which saves”—do they not take place in the organism? We might fill many pages with the mere enumeration of the material conditions surrounding, sustaining, evoking the religious sentiment, as we find it _in fact_ in contemporary life, or in history. Nothing is more chimerical than to conceive religious emotion as an unmixed act, a psychological entity existing in and by itself, independently of its physiological concomitants.