To plead the organic causation of a religious state of mind, then, in refutation of its claim to possess superior spiritual value, is quite illogical and arbitrary, unless one have already worked out in advance some psycho-physical theory connecting spiritual values in general with determinate sorts of physiological change. Otherwise none of our thoughts and feelings, not even our scientific doctrines, not even our dis-beliefs, could retain any value as revelations of the truth, for every one of them without exception flows from the state of their possessor's body at the time.

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