Who does not see that we are likely to ascertain the distinctive significance of religious melancholy and happiness, or of religious trances, far better by comparing them as conscientiously as we can with other varieties of melancholy, happiness, and trance, than by refusing to consider their place in any more general series, and treating them as if they were outside of nature's order altogether?

Lecture I, "Religion and Neurology" - The Varieties of Religious Experience (1902)