Varieties of Religious Experience by William James (1842 - 1910)

The Varieties of Religious Experience: A Study in Human Nature is a book by the Harvard psychologist and philosopher William James that comprises his edited Gifford Lectures on "Natural Theology" delivered at the University of Edinburgh in Scotland between 1901 and 1902. These lectures concerned the nature of religion and the neglect of science, in James' view, in the academic study of religion. Soon after its publication, the book found its way into the canon of psychology and philosophy, and has remained in print for over a century. (Summary by Wikipedia)