This compendium of introductory essays invites scholars and clinicians to better understand people of various faiths from around the world. It is intended to correct the tendency among scientists to study religious behavior without accounting for its human dimension. For example: a psychologist describes a religious ceremony in a certain community as a "sociological phenomenon." Such a technical description is likely to strike members of that community as an attempt by science to explain away their beliefs. This is counterproductive. In order to work effectively and empathetically with people of faith, psychologists should seek an intimate knowledge of how religion operates in the hearts and minds of living, breathing human beings.