It's bad luck to be superstitious
Paradoxically, it is reasonable to be superstitious even though superstitions are not based on reason.
Classical decision theory, not to mention common sense, says we believe a superstition if the cost of believing is less than the cost of missing a real association. For example, don't walk under a ladder since the cost, in terms of effort to walk a little bit further around the ladder, is lower than the cost of replacing your head if a roofing tile falls on it.
Make the sign of the cross if a black cat crosses your path1, since these are shape shifters and familiars of evil spirits and curl up like snakes on the hearths of witches. If you ignore this advice you could succumb to a fatal illness.
Well, certainly if a cat walks across your food preparation area, you increase the risk of having gastric ulcers (from helicobacter pylori - a sort of tiny helicopter flown by a demented bacterium). Fleas are enough justification for avoiding cats, whatever the colour, but cats can cause much more harm than those tiny itchy little blood-suckers. Cats can be the source of ringworm, campylobacter (bacteria in a tent), streptococcus (causing you to strip to your coccyx), salmonella (sounds fishy) and rabies; none of which are very nice. They can cause schizophrenia2, conjunctivitis, tonsillitis, pharyngitis, toxoplasmosis... the scary list of nasties is pretty long.
So it make sense to avoid all cats; not just black cats that cross your path.
Less understandable, however, are superstitions such as the old Aztec custom to sustain the Universe. Every three weeks, these Mesoamericans dragged victims to the top of a pyramid/temple, sliced open their chests and held up the still-beating heart to the gods.
This was less to do with common sense and more to do with bullying by the tribal leadership, keeping the people in line by spinning them a horror story. The 2004 movie 'The Village' shows a good modern example of this. The 2003 invasion for Iraq's Weapons Of Mass Destruction is another. We know better now3.
There are many instances of Church leaders being guilty of similar bullying.
But take care not to confuse religion as just a turbo-charged superstition. A superstition could paint itself pink and do freestyle break-dancing like a mad mongoose, singing "Billions of people follow me. Therefore I am a religion!" But it would still be a humble superstition.
What is the strongest superstition you can think of? How has it, or any other superstition, benefited mankind? What superstition has ever changed somebody's life? (...apart from the above mentioned Aztec victim, of course.)
What superstition has touched the soul?
Superstition is not based on reason but relies on a trust in chance or an irrational fear of what is unknown or mysterious. The cornerstone of religion is love and a trust in Divine Power. There are superstitions within religion of course, but religion is not merely a glorified superstition; it is a consciousness of our personal relationship with the infinite and the eternal.
As humans, we recognise patterns, connect the dots and create meaning from what we see or what we think we see. And when we are not sure if what we see is real, we can be influenced by suggestion from others in a more powerful position, even though there is a cost to us. (See why we create meaning from the meaningless.)
Having said that, as mankind's intelligence develops, as our lives become less threatened by natural woes, the need for superstitious beliefs is less beneficial than in the past. This doesn't mean superstitions are groundless or that it's only a matter of time before they become obsolete. Superstition will be a human trait for many more generations yet.
The previous section showed that religion and superstition are different, yet the wisdom of following certain superstitions mentioned at the top of this page can also be applied to religion.
Blaise Pascal argued that you should believe in God, even if you assume there is no God. The potential benefits of belief make betting on theism rational. Belief offers the believer comfort on earth and everlasting life in heaven. There are, of course, far better reasons and a far more convincing basis for faith in God's existence, but Pascal's Wager4 should give enough for any intelligent skeptic to consider; even though such consideration will not likely lead to belief5.
As part of man's evolution, the superstitions which developed alchemy resulted in the powerful science we understand and use to our benefit today. Science has superseded many things which were the realm of religion in days gone by.
Science has been able to prove many of its theories, but has not disproved superstition (or religion). Scientists may scoff at superstition, but have they ever tested it? Has anyone produced statistics or even studied the incidence of good fortune experienced by people who keep a rabbit's foot under their pillow or a horseshoe on their doorpost, compared with people who break a mirror without throwing salt over their shoulder? Or have scientists just dismissed the whole thing as bunkum without trying to prove it's bunkum. Now that's not very scientific, is it?
One of the few areas of modern scientific research into superstition is the study of 'obsessive compulsive disorder' (OCD). The cause is not yet fully understood; genetic make up, traumatic childhood and bacterial infection, have been suggested.
Many elite actors, musicians and athletes engage in peculiar rituals before a performance. US National Football League player Curtis Martin reads Psalm 91 before every game. And under Michael Jordan's Chicago Bulls livery, he always wore his old North Carolina team shorts. These superstitions may help them control anxiety and OCD traits may even be a pre-condition for such artists and athletes to endure the abnormal hours of repetitive training.
This is not to say that all elite artists and athletes have OCD, or that all people with OCD can excel in art or sport. Research has just scratched the surface of this area. More research needed; perhaps with the obsession of somebody with OCD.
Science has superseded many superstitious and religious ideas6. Yet there are still imponderables, the wonder of consciousness, for example, which help sustain the need for humans to have beliefs beyond those that science can prove.
See also What is luck?