Ludwig Feuerbach

The most important person you've never heard of. A 19th-century German philosopher, his most important work is Die Wesen des Christentums, (The Essence of Christianity), written in 1841. In this book he lays out the basic psychological argument of atheism since that time--that God is a projection of humanity's sense of the infinite. Feuerbach argues that humans are unable to accept their own potential and so they limit themselves by projecting their ultimate potential onto an Other such as God. Instead, Feuerbach says that humanity should come to terms with its own capacity and use it, rather than wasting time worshipping a figment of its own collective imagination.

Feuerbach was a direct influence on Karl Marx and indirectly shaped the psychoanalysis and existentialism, as well as the thinking of millions of college students and would-be iconoclasts.

One neat thing Feuerbach said:

Hegel said "Man is God self-alienated" -- Feuerbach reversed this to say that "God is Man self-alienated." This more or less means that God is all the ideals Man could not achieve projected onto something until it turned into its own thing. For Feuerbach, this is a bad thing. He thought that as long as we humans continued to alienate ourselves toward some God, we could not achieve our own being.

Parts of some of this are from 'Looking at Philosophy' by Donald Palmer

One of the things I have heard throughout my life which has shocked me with a startling clarity, articulating what I have been thinking, this whole time, is something Feuerbach has said:

"We project all our unrealized perfection onto an imaginary non-human entity, God,instead of concerning ourselves with the realizable improvements of our fellow human beings".

The are a number of problems with Ludwig's argument for atheism. The first is one of the most common errors in this kind of argument and that is the presupposition that a god must be the classical Judeo-Christian omnipotent, omniscient, infinite god. There are an amazing variety of gods out there in all shapes, sizes, and flavors who this argument doesn't necessarily apply to. This could easily be fixed by modifying his argument to consider it just against this certain type of god; however, then it would no longer be an argument for atheism but simply against the Christian type god.

Furthermore, this argument only considers one effect of the belief, that being the resultant sense of inadequacy that comes from projecting your infinite potential onto/into something else. It ignores an enourmous amount of other effects of religion; granted some of these are good while some are worse, but they must still be considered in such an argument. It even ignores the other psychological effects such as the added confidence in the belief that god is on your side

As an aside, I myself am an agnostic who feels that the whole religion thing isn't worth it most of the time; however, you can probably get a better argument against Christianity from Bertrand Russel's Why I am not a Christian, although I can't remember if he uses this type of argument along with everything else.