Paul C. Vitz published "Faith of the Fatherless, The Psychology of Atheism" (1999) to question the projection theory of religion. He turns Freud's version of the theory back on Freud by questioning the relationships of many leading atheist thinkers with their fathers. The projection theory attempts to explain the prevalence of religious beliefs in all human societies in terms of individual and collective psychology. In its simplest form, the theory is that human beings invented God and invested him with attributes corresponding to the conventional morality of any given culture. Ludwig Feuerbach, the German Romantic philosopher theorized that human beings unconsciously respond to the uncertainty of life by dreaming of a powerful god and projecting human attributes onto the dream-image. Marx, a student of Feurbach, used a variation of the same idea in his communist attack on religion as the opiate of the masses. Freud put the theory in terms of wish fulfillment. He said humans fulfilled powerful emotional wishes for safety against powerful forces in an impersonal universe - responding to rational fears by irrational beliefs in a non-existent being. The theory, in all of its variations, has become part of the conventional wisdom of the anti-religious.
Ironically, the projection theory is an atheist extrapolation of certain streams of religious thought. There has been a tension between prophecy and priesthood within Judaism, Christianity, Islam and other religions, with an awareness that religion is often allied with mighty and the wealthy against the interests of the common person and that religious arguments are often made in support of purely political and economic positions. At a deeper level, human beings have a rich history of religious diversity. Most religions have a set of explanations - ignorance, sin and the confusing work of diabolic powers - for why other people happen to be worshipping idols and false gods. The idea that other people might be corrected by rational discourse and led to the truth is closely related to the religious idea of converting and saving the heathen. It is rooted in the ideas that God has endowed the stranger with the capacity to know the truth, and that God loves the stranger enough to want to save him. Within the history of ideas, the atheist version of rationalism seems to have been taken from the religious version.