"...For the hypotheses need not be true nor even probable. On the contrary, if they provide a calculus consistent with observations, that lone is enough." -- a theologian's foreword to the first edition of Nicolaus Copernicus's De Revolutionibus Orbium Coelestium, which introduced the heliocentric theory to Europe and greatly expanded it, 1543.

"This textbook contains material on evolution. Evolution is a theory, not a fact, regarding the origin of living things. This material should be approached with an open mind, studied carefully, and critically considered." -- Sticker on biology textbooks in Cobb County, Georgia, 2001 - 2005

Someone with a naturalistic worldview may wonder how an otherwise sane, rational adult can believe in a religion that has been proven to be less and less likely and more and more redundant with each new scientific discovery, be it Judaism with its vengeful god, Buddhism with its reincarnation, or Scientology with its galactic overlord Xenu.

Our knowledge of how our brains work, where we come from, and where we are is being expanded daily by studies in neurology, genetics, and astronomy to name just a few disciplines that provide real insights. In spite of all the evidence to the contrary, however, many people still cling to superstitious beliefs about what we are and how the universe works. It's clear that logical arguments based upon observed facts about the universe do nothing to sway people from such beliefs.

Some people still refuse to accept that we evolved from other hominins, for instance, just as some people used to refuse to accept that the Earth evolves around the sun, stating that there must be some sort of flaw in the evidence that supports this fact, or the methodology of examining it. In both cases, this is obviously not because they have looked at the available evidence and made an informed decision. So what can cause someone to cling so rigidly to their beliefs that they are unwilling to shed them in light of contradictory evidence?

In other words, how can a thinking, rational adult be religious?

This question makes two mistaken assumptions about how people choose their religion: firstly, that they do so rationally; and secondly, that they do so as adults.

"I want to believe" -- Poster, The X-Files

In Malcolm Gladwell's book Blink, he talked about a world expert in archaic sculpture by the name of Ernst Langlotz, who could easily spot a fake, with one exception: a single bronze statuette, one of the first pieces of art he acquired. Perhaps he fell in love with it, suggested art historian George Ortiz, whom Langlotz had once offered to sell the statuette to, and perhaps that long lasting love had clouded his judgement, even though he could be so rational about other fakes, seeing them for what they were.

In Richard Dawkins's book The God Delusion, he told a similar story of a prominent Cambridge theologian. While having dinner with the anthropologist Pascal Boyer, the theologian commented on the absurdity of other people's irrational beliefs despite himself presumably believing in someone who can telepathically communicate with every human on the planet simultaneously, but won't do anything to help them.

I think these are perfect examples of how the human mind works: we can see everything as it truly is, except things we hold dear.

As a species, us humans are indeed capable of rational thought, but we'd be deluding ourselves if we assumed that all our decisions were made consciously by logically weighing up the pros and cons of the available options, or by looking at which theory the available evidence proves. With effort, we can train ourselves to think this way, but it's not our default way of thinking.

Instead, a lot of the time we just decide to do what feels better. We stick with what's familiar and comfortable. We defend what we have fond memories of and what's worked well for us in the past. We favour what seems intuitive. This has nothing to do with what is correct, and everything to do with what has personally served us well before.

You can use all sorts of complex mental gymnastics to avoid confronting the absurdity of a mistaken belief that you hold dear, whether that belief is in magick or gods. The reason you'd want to put in so much mental effort to do this, however, likely has a lot more to do with your desire to believe in something than it has to do with any logical arguments or observations about reality.

Some people just plain want to believe stories about an omnipotent parent figure who can dish out justice to anyone while "lovingly" watching over them, even if the parent figure in question is an abusive one. Others want to believe that the universe will magically dish out justice of its own accord. Pretty much everyone wants to believe that she will live forever, that we're special as a species, and that we're not alone. It's not surprising that these themes are common ideas that have formed the basis of many religions.

"Hook 'em while they're young." -- Cardinal Glick, Dogma

Very few people start to delude themselves with a religion once they're an adult. Those who do usually do so because they need a mental crutch as they're breaking free of an antisocial addiction, coming to terms with with the death of a loved one, or getting through a painful divorce. Religious people use all of these opportunities to convert people.

Indeed, a religious person trying to convert someone while she's grieving over the death of a loved one seems the worst of these, as in the case of religion and spirituality, the promise of eternal life may hinder the grieving process, and at any rate is in very bad taste. This is bad enough with tales of heaven or reincarnation, and downright abhorrent when a so-called medium pretends - or, in rare cases, genuinely believes - they can talk to the deceased person in question.

However, the vast majority of loyal members become such during their childhood, when they're too young to question their parents' advice. This is why the three Abrahamic religions condemn contraception and anything else that would let people have the fun of sex without the hassle of producing more children to indoctrinate. It's why religious parents send their children to separate schools where they can be indoctrinated with whichever religion they happen to believe is the one true faith.

It would be nice if ideologies didn't target such vulnerable people. This seems unlikely to happen though, as any ideologies that allow consideration towards the humans that believe in them will merely be weeded out by their evolution to make way for other ideologies that aren't afraid to get away with whatever they can in the name of expansion.

In conclusion, we don't always make rational decisions. Far more frequently, we make emotional ones, then try to justify them later on by coming up with plausible sounding arguments for them.

The reason a thinking, rational adult can be religious is usually that she was indoctrinated when she was either very young or in some other way vulnerable, and as a consequence, dependent.

The reason a thinking, rational adult can stay religious is either that she's ill informed, or, more likely in this day and age, that she's more comfortable ignoring the facts we now know about life and how the universe works than she would be embracing the change in her worldview necessary to see the world as it truly is. She likely has a lot of emotions and experiences tied up with her idea of what her religion is, and her religion may even be a part of her own identity. These feelings are far more compelling than cold facts about the universe.

"The universe is unbelievable. Our galaxy, the Milky Way, a hundred billion stars. A hundred billion stars! We wouldn't count up to a hundred billion! We could count up to a hundred billion, but we would not. They have clusters of galaxies, and then these big bits of nothing. So it's awesome, yeah? The universe is awesome using the original version, the meaning of the word awesome." -- Eddie Izzard, Circle

I suspect the main flaw in the thinking of people like Richard Dawkins is that he seems to expect a rational argument to be able to convince someone to pluck up the courage to make that change in their worldview necessary to break free.

Maybe a better strategy would be to point out how beautiful the universe truly is, from the elegant way bacteria communicate with one another to the beautiful dance of the planets, stars and galaxies. Maybe then people will realise the universe is far from lonely or random, but rather a beautiful, majestic place, that turns out to be even more literally wonderful and awesome with each new thing we learn about it.

Update: OK, it looks like it's mostly Catholicism and Orthodox Judaism that don't allow contraception, so I have to let most Muslim, Protestant and Jewish variations off the hook in this regard, although this doesn't necessarily mean they condone people having sex for fun, and some religions that allow contraception still require it to be in the context of a marriage. Maybe I should have used the example of gay sex instead...