 James hints at his religious concerns in his earliest essays and in The Principles, but they become more explicit in The Will to Believe and Other Essays in Popular Philosophy (1897), Human Immortality: Two Supposed Objections to the Doctrine (1898), The Varieties of Religious Experience (1902) and A Pluralistic Universe (1909). James oscillated between thinking that a “study in human nature” such as Varieties could contribute to a “Science of Religion” and the belief that religious experience involves an altogether supernatural domain, somehow inaccessible to science but accessible to the individual human subject. 