Richard Dawkins, Steven Weinberg, Sam Harris, AC Grayling, Polly Toynbee ... I expect that most writers who have tried to interview an equivalent stellar cast have found that their phone calls went unanswered and their emails were assigned to the Trash Box. But there's something about the perceived irrationality of belief in God which brings many atheists out fighting.

The religious sometimes wonder why anyone would choose not to believe in God. But, as Sam Harris told me, it is they who must shoulder the burden of proving their case. After all, "every Christian can confidently judge the God of Zoroaster to be a creature of fiction, without first scouring the universe for evidence of his absence."

For Harris all that one needs to banish false knowledge is to recognise an absence of evidence. And there is one hymn sheet from which even atheists are willing to sing: that headed "Lack of Evidence". For instance Richard Dawkins told me that he doesn't believe in leprechauns, pixies, werewolves or a whole range of gods, and for the same reason in every case: "there is not the tiniest shred of evidence for any of them, and the burden of proof rests with those who wish to believe."

Particle physicist Victor Stenger added that the God of Jews, Christians and Muslims supposedly plays such an important role in the universe that there should be evidence that he exists. But instead, "there is nothing in the realm of human knowledge that requires anything supernatural, anything beyond matter, to describe our observations."

But it's not just an absence of evidence upon which several atheists relied. Rather, there was perceived to be clear evidence which suggests that God is no more real than an imaginary friend. The clearest pointer seems to have been suffering. No wonder that Polly Toynbee told me that the only time that she is ever tempted, momentarily, to believe in God "is when I shake an angry fist at him for some monstrous suffering inflicted on the world for no reason whatsoever."

Some believers - and Christian philosophers - respond that suffering on earth actually enriches our lives. But as psychologist Richard Wiseman told me, if that were so, it would paint a picture of heaven being a rather miserable place. For other believers, it may be that God has a very good reason for allowing suffering but we can't understand what it is because we lack his divine knowledge. Biologist Jerry Coyne gives this argument short shrift: "If there is a god, the evidence points to one who is apathetic - or even a bit malicious."

Publisher and author Michael Shermer gave me an intriguing overview to the question of God's existence:

"In the last 10,000 years there have been roughly 10,000 religions and 1,000 different gods; what are the chances that one group of people discovered the One True God while everyone else believed in 9,999 false gods?"

When it comes to the God Debate, one can't ignore the commodity to which the religious cling to sustain their beliefs: faith. Several months ago, I carried out an equivalent investigation when I asked many prominent Christians to give me their reasons for belief. Several of them admitted that it must ultimately come down to whether you take it on faith; once you do, you'll experience God's love and you won't worry about having the answer to every intellectual argument.

For many believers, faith is all that matters, shielding them from arguments and evidence which they would rather not have to consider. These are the ones who oppose the Critical Thinking of science and prefer the Critical of Thinking inherent in their faith.

But if you rely on blind faith, what are the chances that you're going to see the light?

For others, their religion satisfies them intellectually. Yet when they can't reason their way past specific problems (say, suffering or biblical inconsistencies), their faith comes riding to the rescue. But faith is hardly a white horse: more like a white elephant, trumpeting a refusal to engage in debate as though it were something about which to be proud.

The atheists that I spoke to are the products of what happens to many intelligent people who aren't prepared to take important decisions purely on faith, and who won't try to believe simply to avoid familial or societal pressures. And as philosopher Daniel C. Dennett put it: "Why try anyway? There is no obligation to try to believe in God."

I could hardly end this piece without mentioning PZ Myers who evidently managed to dig out a metaphorical old joke book from his vast collection of weighty tomes about the God Debate:

"Religious beliefs are lazy jokes with bad punchlines. Why do you have to chop off the skin at the end of your penis? Because god says so. Why should you abstain from pork, or shrimp, or mixing meat and dairy, or your science classes? Because they might taint your relationship with your god. Why do you have to revere a bit of dry biscuit? Because it magically turns into a god when a priest mutters over it. Why do I have to be good? Because if you aren't, a god will set you on fire for all eternity. These are ridiculous propositions. The whole business of religion is clownshoes freakin' moonshine, hallowed by nothing but unthinking tradition, fear and superstitious behavior, and an establishment of con artists who have dedicated their lives to propping up a sense of self-importance by claiming to talk to an invisible big kahuna."

Amen to that.