The following is excerpted from an interview with American Atheists (the full text can be found at Atheists.org).
On 'radical atheism':
"If you describe yourself as "Atheist," some people will say, "Don't you mean 'Agnostic'?" I have to reply that I really do mean Atheist. I really do not believe that there is a god - in fact I am convinced that there is not a god (a subtle difference). I see not a shred of evidence to suggest that there is one. It's easier to say that I am a radical Atheist, just to signal that I really mean it, have thought about it a great deal, and that it's an opinion I hold seriously. It's funny how many people are genuinely surprised to hear a view expressed so strongly. In England we seem to have drifted from vague wishy-washy Anglicanism to vague wishy-washy Agnosticism - both of which I think betoken a desire not to have to think about things too much."
On the burden of proof:
"I don't accept the currently fashionable assertion that any view is automatically as worthy of respect as any equal and opposite view. My view is that the moon is made of rock. If someone says to me "Well, you haven't been there, have you? You haven't seen it for yourself, so my view that it is made of Norwegian Beaver Cheese is equally valid" - then I can't even be bothered to argue. There is such a thing as the burden of proof, and in the case of god, as in the case of the composition of the moon, this has shifted radically. God used to be the best explanation we'd got, and we've now got vastly better ones. God is no longer an explanation of anything, but has instead become something that would itself need an insurmountable amount of explaining. So I don't think that being convinced that there is no god is as irrational or arrogant a point of view as belief that there is. I don't think the matter calls for even-handedness at all."
On the arguments for religious ideas, contrasted with those for evolutionary biology:
"What astonished me, however, was the realization that the arguments in favor of religious ideas were so feeble and silly next to the robust arguments of something as interpretative and opinionated as history. In fact they were embarrassingly childish. They were never subject to the kind of outright challenge which was the normal stock in trade of any other area of intellectual endeavor whatsoever. Why not? Because they wouldn't stand up to it. So I became an Agnostic. And I thought and thought and thought. But I just did not have enough to go on, so I didn't really come to any resolution. I was extremely doubtful about the idea of god, but I just didn't know enough about anything to have a good working model of any other explanation for, well, life, the universe and everything to put in its place. But I kept at it, and I kept reading and I kept thinking. Sometime around my early thirties I stumbled upon evolutionary biology, particularly in the form of Richard Dawkins's books The Selfish Gene and then The Blind Watchmaker and suddenly (on, I think the second reading of The Selfish Gene) it all fell into place. It was a concept of such stunning simplicity, but it gave rise, naturally, to all of the infinite and baffling complexity of life. The awe it inspired in me made the awe that people talk about in respect of religious experience seem, frankly, silly beside it. I'd take the awe of understanding over the awe of ignorance any day."
A popular Adams quote often applied to atheism and the superfluousness of religion is:
"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?"
Ironically, in its original context, the "garden" in question does turn out to have "fairies" at the bottom of it. It comes from The Hitch Hikers Guide To The Galaxy when Ford is dismissing Zaphod's belief that they are orbiting the "legendary" planet of Magarathea - which it turns out that they are.