William James
William James (1842–1910) is regarded by most psychologists of religion as the founder of the field. 

In the psychology of religion, James' influence endures. His Varieties of Religious Experience is considered to be the classic work in the field, and references to James' ideas are common at professional conferences.

• James distinguished between institutional religion and personal religion.
• Institutional religion refers to the religious group or organization and plays an important part in a society's culture.
• Personal religion, in which the individual has mystical experience, can be experienced regardless of the culture.
• James was most interested in understanding personal religious experience.

• In studying personal religious experiences, James made a distinction between healthy-minded and sick-souled religiousness.