Melbourne hosted the Global Atheist Convention this past weekend, where for three days a coterie of the faithless urged each other on in their collective scepticism. The most famous proponents of a godless universe were in attendance – Richard Dawkins, Sam Harris and Daniel Dennett – but this time, sadly, the most engaging and entertaining of them, Christopher Hitchens, wasn't.
The convention sought to ''Celebrate Reason'', which seems, well, reasonable enough. We all need something substantial on which to make our judgments, and according to those who attended, it's the clear thinkers, those unencumbered by superstition and religious nonsense, who are most likely to arrive at the truth.
But while it's easy to mock those with religious beliefs, the atheist appeal to a thoroughly rational, objective position is not without its problems.
Daniel Kahneman, arguably the most influential psychologist alive today, is a Nobel prize winner in economics. He's also the author of Thinking, Fast and Slow, where he draws upon a lifetime of studying human behaviour that has shown him just how unreliable the human mind really is.
Along with his late colleague Amos Tversky, Kahneman's at times bizarre experiments have helped provide a framework to understand why, for instance, applicants to medical school are less likely to be admitted if interviewed on a rainy day. And why judges, when asked to roll a pair of dice rigged to come up three or nine before the mock-sentencing of a shoplifter, decided to give the ''offender'' an average of eight months if they rolled nine and five months if they rolled three.
But here's the thing. While Kahneman and Tversky reveal what appear to be permanent fallibilities in human reason, their rule of thumb was that they would study no specific example of human ''idiocy or irrationality'' unless they first detected it in themselves. In other words, even experts suffer the same quirks of human unreason as anyone else.
This could, I suppose, be fuel for the religious sceptic's fire – suggesting that those who put their faith in things unseen are clearly deluding themselves. But it cuts both ways. The same thing applies to non-believers whose hopes and aspirations might cloud their judgment on the question of God's existence.
And there remain formidable challenges for the enthusiasts of non-belief. Renowned American philosopher Alvin Plantinga's most famous, novel and ironic argument is that naturalism cannot rationally be believed.
The argument is a bit complex but it goes something like this: if you're a naturalist (there's no God or gods), you'll also be a materialist (the only thing that exists, including consciousness, is physical matter). You'll think human beings are material objects, and that there isn't any immaterial soul, or self, or person.
If you think this way, you will also necessarily think that any belief (''all religion is irrational'', for instance) is something like a structure of neurons in the nervous system, or in the brain, which will have two kinds of properties: the belief will have neuro-physiological properties, but it will also have content properties, meaning there's a purely physical cause for something you believe.
Now, evolution couldn't give a toss about what you believe. It cares about rewarding adaptive behaviour and punishing maladaptive behaviour. So evolution will gradually modify those neuro-physiological properties in the direction of greater adaptiveness, but it doesn't follow that it modifies belief in the direction of truth. Evolution doesn't care about true belief.
So, if you accept the combination of naturalism and materialism, says Plantinga, you'll have to accept that any particular belief you might hold could as likely be false as true. The probability that your beliefs are reliable will be low.
If, however, you believe in God and don't accept naturalism and materialism, then that particular problem doesn't apply. You will assume there is a being who is separate from creation but speaks truth into the fibre of the universe. Sure, you'll have other challenges to your faith, but you'll have a reason to trust your faculties in a way that the naturalist does not. Believing in human rationality is quite rational within a theistic world view, but not so in an atheistic framework.
Plantinga is quick to point out that none of this is intended to prove belief. There remain serious questions for those who believe in an all-powerful, good God who creates and sustains the universe, and believers need to face these.
But Plantinga's thesis might prompt those in the ''all religion is delusional'' camp to approach vital questions of human existence with measured consideration of the alternatives – something beyond naked contempt. That, surely, is a reasonable request.
Simon Smart is a director of the Centre for Public Christianity.