the Middle Ages. But it will serve as a figure of the growth of religion generally. Priestcraft, for instance, fastened upon religion parasitically when it became sappy enough to support a parasite and later struck its own roots in the soil.
But let us first attach a precise meaning to "the psychology of religion." It is a clumsy phrase. I use it only because it is familiar, but psychology is the whole science of mental behavior, not an interpretation of a particular thing. And what do we mean by "religion"? The objective body of doctrines, rituals, and priesthoods, or the subjective acceptance of them? I have, in any case, dealt in other Little Blue Books with the evolution of religion in the objective sense. We mean here religion as an attitude of belief and emotion. And again we have to ask, whose? There is almost nothing in common between the mental attitude of a liberal professor of theology at Chicago and of a peasant in southern Mexico, of a Theistic scientist and a Roman Catholic laundry woman or housemaid. All that we can do here is to take two broad classes, the ordinary and the intense or fanatical believer, with a few variations within each class, and analyze the mental attitude.
For the first class, the great mass of religious people throughout the world, there is a good deal of truth in the new theory to which I referred. Ten years ago a book entitled Instincts of the Herd in Peace and War (1916), by W. Trotter, was widely discussed. That period of intense collective emotion very nat-
