In a discussion between religious believers and atheists there are two fundamental questions: whether a particular faith is actually true or whether (irrespective of truth) faith can be an overall force for good in the world. For the first question it is quite difficult for a believer to respond to the charge that not all faiths can be true, and the charge that one's particular faith is almost always determined by one's cultural background. But the second question is more subtle: it depends on what you count in the balance sheet. Which wars should you count as being religiously motivated? If, on the surface they were religiously motivated (like the Thirty Years War), would they have occurred even if religion had mysteriously disappeared from the human condition? Nevertheless, most theists will concede that, in the past, many things have been done in the name of religion that nowadays we abhor.
Often such a concession is accompanied by two mitigating comments: that nowadays religion is more benign, and that much community good work is carried out by churches. I accept both of these comments, am happy to discount the past and to make a balance sheet purely on today's religious activities.
In this post I am not going to point to the many examples around the world where violence and intolerance are founded on religious grounds. Nor am I going to criticise the many well-meaning, sincere church-goers of all faiths who care deeply about their fellow men and women and live their lives trying to improve our society. Instead I wish to make a case that the very presence of faith-based behaviour in our society has negative consequences.
Is it harmless to "touch wood" (you know what I mean, you naughty people) just in case there might possibly be something in that old superstition? Is it harmless to believe that "what goes around comes around" or that "everything happens for a reason"? Is it harmless to believe that your life is overseen by some benevolent creator, or to believe that praying for a friend to recover from an illness is effective? Aren't all those things (and many others like them) at the very worst just personal musings?
In my opinion these beliefs are damaging in a subtle way. The fabric of religious belief contains many strands: the examples I have given are less damaging than some others (such as killing people because of a conviction you think is implanted in you from your god, or refusing a woman birth control because a holy book prohibits it, or marginalising a gay person). But I use the fabric metaphor because these beliefs are connected. If you believe that "everything happens for a reason" you have taken a step along a superstitious strand and you will take another unthinking step a little more willingly. In bad cases you may become so superstitious that you may one day come to believe that you are charged by a god to act in a certain way, and for some fervent believers that way may be bad for society (or bad for you).
In other words what I am claiming is that superstition, or believing things for which there is no evidence, is a pernicious thought habit. Once you let a smidgeon of it pollute you, you are in danger of wading a little deeper into the pollution. Maybe you will resist the next superstitious thought that you meet. But isn't it likely that, having admitted to some unthinking superstition, your critical thinking faculties may let you down once more, or twice more.
If you remain unconvinced consider the prevalence of religious belief in the United States. That rich culture allows many scales of superstition to flourish and some of them are surely harmful. For example Justice Antonin Scala believes that Satan is a real person. Doesn't it make you uneasy that a member of the Supreme Court of the US, someone who has to judge on human wickedness, believes in a superhuman incarnation of evil? Or what about Congressman Paul Broun who is a Young Earth creationist. He is a member of the House Science Committee! Do you trust him to understand the science behind Global Warming (to take just one example). And then of course there are the tele-evangelists who amass large fortunes while promoting hatred of gays (and in some cases like Bob Larson and Ted Haggard are caught in mind-boggling hypocrisy). Of course, these examples are outliers but my point is that such irrational behaviour is only unremarkable in a culture where faith is exalted rather than pitied.
The problems of life are very complicated and superstitious thought patterns are sometimes useful as rough and ready rules of thumb in order for us to make quick decisions (don't walk under ladders so that a paint pot will miss you when it falls). But don't credit your superstitions with mysterious properties or you will lead a less examined life. Socrates thought that such lives were not worth living and I agree.