Is it possible to deny the existence of a god logically, morally, or philosophically?  Many point out that the denial of a god’s existence is simply another form of faith, needing its own rational basis just as surely as believing in a god would. On the other hand, others maintain that the most defensible position is one of disbelief until proven otherwise.

Perhaps one of the best modern books to build a case for the viability of atheism was published in 2006 by Richard Dawkins under the title The God Delusion.  He summarizes his arguments on pages 156 and 157 as follows:

This chapter has contained the central argument of my book, and so, at the risk of sounding repetitive, I shall summarize it as a series of six numbered points.

1. One of the greatest challenges to the human intellect… has been to explain how the complex, improbable appearance of design in the universe arises.

2. The natural temptation is to attribute the appearance of design to actual design itself…

3. The temptation is a false one, because the designer hypothesis immediately raises the larger problem of who designed the designer… It is obviously no solution to postulate something even more improbable [than the design itself]…

4. The most ingenious and powerful [explanation of complexity] so far discovered is Darwinian evolution by natural selection…

5. We don’t yet have an equivalent [theory] for physics. Some kind of multiverse theory could in principle do for physics the same explanatory work as Darwinism does for biology…

6. We should not give up hope of a better [theory] arising in physics, something as powerful as Darwinism is for biology…

[Therefore] God almost certainly does not exist.

To draw out this argument, watch the following video in which Dawkins, speaking at a TED Talk event, makes the case not only for atheism, but also for why atheists should openly declare themselves in public debate and not be ashamed of their position.