How sweet are thy words unto my taste! yea, sweeter than honey to my mouth!
This might be literally true. According to research reported on in the Boston Globe, Christians were more likely to rate a soft drink favourably after copying out a passage from the Bible. The same researcher, Ryan Ritter (a graduate student in psychology) found that less congenial passages left a nasty taste in the mouth.
In one experiment, Christian volunteers were asked to rate a mildly bitter lemon drink. Next, in what they were told was a different study entirely, they were asked to copy out pieces of writing. They were then asked to taste and rate another drink. Those who had been engaged with the Qu'ran and Richard Dawkins' The God Delusion found the second drink more unpleasant than the first one. Those exposed to a neutral piece of writing (an extract from a dictionary) had a less negative or even a positive reaction. In fact, it was exactly the same drink.
In Ritter's other experiment, Christians who had copied from the Qu'ran, but washed their hands afterwards, rated the drink more favourably than those who had not had the opportunity to "cleanse" themselves from contact with the rival religion's scripture. But when they had been copying out a passage from the Bible, the effect of washing their hands was to make them less favourable to the drink. In the latter case, it was almost as though the positive religious vibes from the Bible transmitted themselves through the glass and into the drink -- provided they hadn't been washed away first.
In his paper, Ritter suggests that "these results provide evidence that contact with a rejected religious belief elicits disgust and that both negative and positive moral contagions can be removed through physical cleansing. "
Experiments like these, involving a small sample and carried out under conditions of extreme artificiality, can only ever be indicative, of course. Nevertheless, it does fit in with a growing body of research into the psychological basis of morality.
Psychologists such as Jonathan Haidt have previously suggested a close connection between physical and moral aversion -- that the moral sense works mainly on the level of gut feeling rather than of rational analysis. Things believed to be transgressive or immoral -- such as sexual practices condemned by the prevailing social mores -- are often perceived as being physically disgusting.
Disgust has an obvious biological function: it helps keep us from ingesting toxic or contaminated food or coming into close contact with contagious disease. Likewise, the disgust-response is a powerful means of drawing and maintaining moral boundaries. If just thinking about something makes you feel physically uneasy you're less likely to go ahead and do it.
And of course religion and morality, though far from identical, are closely bound up together. Religious leaders claim expertise in moral matters; many would go further and claim that God is the source of morality, that being good is largely a matter of obeying divine commands. Even where religious precepts aren't explicitly moral in themselves -- as in the case of dietary or dress codes -- transgressing against them may be seen as immoral and certainly evokes the same reactions.
Ryan Ritter's suggestion is that exposure to ideas that challenge one's religious identity -- either by critiquing it directly (as Dawkins does) or offering something in its place (the Qu'ran) -- has a similar effect. It's easy to see how this could be an effective way of keeping people within the fold and unwilling to question traditional beliefs.
But in the modern world, with members of different faiths rubbing up against each other, such visceral attachment to the doctrines and symbols of a religion has obvious dangers. "Can we ever have peace between groups that are fundamentally disgusted by each other?" Ritter asks.
Inter-faith activists pin their hopes for a more harmonious world on members of different religions getting together and realising how much they have in common. They stress that different outward forms and theological structures matter less than what all faiths share -- compassion for others as expressed in the "Golden Rule". Mr Faith himself, Tony Blair, urged a conference in 2009:
Love your God; love your neighbour as yourself. These simple admonitions are the guiding light of our faith. They give us the possibility of 'A Common Word.' When we lose our way, Christians or Muslims, this is the light by which we re-discover our true path.
But it's perhaps misleading to find the common core of religion in moral precepts that religious people share equally with humanists. Religion's deepest appeals are irrational, and they reside in strong feelings of belonging and attachment to particular stories and to fellow believers. Religion isn't just about being generally nice and loving one's neighbour. It's also about the claim that particular beliefs are true, and (just as importantly) about other beliefs not being true.
As society has become religiously plural, faith has become increasingly become a source of identity -- and therefore of division. To be both loyal to one's own traditional beliefs and accepting of others' different (perhaps incompatible) beliefs is the liberal interfaith ideal. But if Ritter is correct, such idealism may run counter to the very nature of faith.
It's a pity, perhaps, that Ritter did not try his experiment out on convinced atheists. Would they have reacted to a Biblical passage as negatively as the Christians reacted to Dawkins? I suspect that they probably would.
Nelson Jones runs the Heresy Corner  blog. He was shortlisted for the 2011 Orwell Prize for blogging.