William P. Alston 
Perceiving God [PDF ebook] 
The Epistemology of Religious Experience

In this clear and provocative account of the epistemology of religious experience, William P. Alston argues that the perception of God-his term for direct experiential awareness of God-makes a major contribution to the grounds of religious belief. Surveying the variety of reported direct experiences of God, Alston demonstrates that a person can be justified in holding certain beliefs about God on the basis of mystical experience.