There are actually 16 basic human psychological needs that motivate people to seek meaning through religion, said Steven Reiss, author of the new theory and professor of psychology and psychiatry at Ohio State University.
These basic human needs - which include honor, idealism, curiosity and acceptance - can explain why certain people are attracted to religion, why God images express psychologically opposite qualities, and the relationship between personality and religious experiences.
Previous psychologists tried to explain religion in terms of just one or two overarching psychological needs. The most common reason they cite is that people embrace religion because of a fear of death, as expressed in the saying 'there are no atheists in foxholes," Reiss said.
"But religion is multi-faceted - it can't be reduced to just one or two desires."
Reiss described his new theory - which he said may be the most comprehensive psychological theory of religion since Freud's work more than a century ago -- in the June issue of Zygon, a journal devoted to issues of science and religion.
"I don't think there has been a comprehensive theory of religion that was scientifically testable," he said.
The theory is based on his overall theory of human motivation, which he calls sensitivity theory. Sensitivity theory is explained in his 2000 book Who Am I? The 16 Basic Desires that Motivate Our Action and Define Our Personalities (Tarcher Putnam).
Reiss said that each of the 16 basic desires outlined in the book influence the psychological appeal of religious behavior. The desires are power, independence, curiosity, acceptance, order, saving, honor, idealism, social contact, family, status, vengeance, romance, eating, physical exercise, and tranquility.
In fact, Reiss has already done some initial research that suggests the desire for independence is a key psychological desire that separates religious and non-religious people. In a study published in 2000, Reiss found that religious people (the study included mostly Christians) expressed a strong desire for interdependence with others. Those who were not religious, however, showed a stronger need to be self-reliant and independent.
The study also showed that religious people valued honor more than non-religious people, which Reiss said suggests many people embrace religion to show loyalty to parents and ancestors.
In the Zygon paper, Reiss explains that every religious person balances their 16 basic human needs to fit their own personality.
"They embrace those aspects of religious imagery that express their strongest psychological needs and deepest personal values."
One example is the desire for curiosity, Reiss said. Religious intellectuals, who are high in curiosity, value a God who is knowable through reason, while doers, who have weak curiosity, may value a God that is knowable only through revelation.
"People who have a strong need for order should enjoy ritualized religious experiences, whereas those with a weak need for order may prefer more spontaneous expression of faith," he said.
"The prophecy that the weak will inherit the earth should appeal especially to people with a weak need for status, whereas the teaching that everybody is equal before God should appeal especially to people with a strong need for idealism."
If religion and personality are linked, religion must provide a range of images and symbols sufficiently diverse to appeal to all the different kinds of personalities in the human population, Reiss says. Religious imagery potentially accommodates everybody because in many instances the images and symbols are psychological opposites.
"How we value and balance the 16 psychological needs is what makes us an individual, and for every individual there are appealing religious images," he said.
"The values that guide a personality with a strong need for vindication are expressed by a God of wrath, or a war God, while the values that guide a personality with a weak need for vindication are expressed by a God of forgiveness."
"The values that guide a personality with a strong need to socialize are expressed by religious fellowship and festivals, while the values that guide a personality with a weak need to socialize are expressed by religious asceticism."
The need for acceptance makes meaningful images of God as a savior, while its opposite inspires the concept of original sin, according to Reiss. The need to eat motives some people to value abstinence and others to value sustenance.
"Because this theory can be tested scientifically, we can learn its strengths and weaknesses, and gradually improve it," Reiss said. "Eventually, we may understand better the psychological basis of religion."
Reiss emphasized that the theory addresses the psychology of religious experiences and has no implications for the validity or invalidity of religious beliefs.