威廉·詹姆斯（William James，1842—1910）美國本土第一位哲學傢和心理學傢，也是教育學傢，實用主義的倡導者，美國機能主義心理學派創始人之一，也是美國最早的實驗心理學傢之一。1875年，建立美國第一個心理學實驗室。1904年當選為美國心理學會主席，1906年當選為國傢科學院院士。2006年，詹姆斯被美國的權威期刊《大西洋月刊》評為影響美國的100位人物之一（第62位）。

Hailed as "one of the greatest philosophical minds of all time" by English philosopher Alfred North Whitehead, William James is widely recognized as one of the most influential figures in twentieth-century Western philosophy and as the founder of the psychology of religion.

An immediate bestseller upon its publication in June 1902, The Varieties of Religious Experience weaves together acute observations with simple anecdotes to argue that individual religious experiences, rather than the tenets of organized religion, are what form the backbone of religious life. The book explores all sides of religous life, from repentance and conversion to mysticism and the value of saintliness. Written with James' characteristic humor and skill, The Varieties of Religious Experience sounds the depths of what he termed "Man's Religious Appetites.

The old clich that Henry James wrote novels as though they were philosophical treatises whereas William James wrote philosophic treatises as though they were novels, while unfair to Henry, describes . . . the William James of The Varieties of Religious Experience, very well. Believers and unbelievers (and semibelievers) will continue to find in it both a resource and a challenge," wrote religion scholar Jaroslav Pelikan.