A religion that is good for anything must not only be one that is intelligible and reasonable, but must satisfy the spiritual cravings, and also exercise moral control over the animal nature. At the same time, it is liable to undue stress in each direction; it may become a mere theological speculation, mere mysticism, or resolve itself into exterior formalism. Whenever it manifests a preponderating tendency in one or other of these directions--the element in man that is not given its adequate scope will revolt, and fling itself into an opposite scale. The function of the reason in religion is to act as the balance wheel of the spirit. Reason is not the mainspring, not the motive power of religion; it is its controlling, moderating faculty. Throughout the history of mankind we are coming continually upon phenomena of a spiritual nature, outbursts of the spiritual faculty in strange and often in very repulsive manifestations, and it may not be amiss to look at some of these and to learn what is their real nature. Among the primitive races which at this day represent the earliest phases of psychological development, the savage man has a vague apprehension of the existence of a spiritual world, haunted by the souls of the dead which have not been absorbed into the universal spirit from which they emanated. He has no definite belief, he has only an apprehension. In the spiritual world, the existence of which he suspects, there is no system; concerning it he has no doctrine. Its existence implies no responsibilities. Even the idea of an all-pervading spirit is inchoate. All that man is confident about is that he is surrounded by and subject to the influences of spirits, now beneficent, then malevolent, always capricious, that have to be humoured and propitiated, and that allow themselves to be consulted. There is but one, so to speak, natural mode of holding intercourse with the spirits, and that is by ecstasy, whether natural or superinduced by narcotics. The man who falls into hysterics, the man who is cataleptic, is the natural priest. An hysterical, a cataleptic condition, is not understood, and just as the unusual and contorted bit of wood or stone receives reverence as a fetish, so does the man subject to unusual fits become a priest. To him the man of less nervous organism applies when he desires to hold intercourse with the unseen world. Incantation, whereby the hysterical work themselves into hysteria, and religious rite are one. The Shaman or Medicine-man is the only priest. Indeed, there is not a people, at a low stage of mental and moral development, among which this phase of religion is not found, before the spirit world coagulates into distinct beings, the rudiments of a theology appear, the priesthood emerges as a caste, and worship is fixed in ceremonial observance.