After scientific verification, the other significant way of estimating evidence is the legal approach. At law, there must be a witness or a piece of evidence. It doesn’t matter how hard you believe something, if you have neither witnesses nor evidence, then you don’t have a court case.

Criminal cases are meant to be resolved ‘beyond a reasonable doubt’, though there are many judges who have allowed juries to send people to prison where there was reasonable doubt, because it later turned out that the defendants were innocent.

Civil cases are resolved by the ‘balance of probabilities’, and this is closer to the test that we use for most of our information. Very few people research exhaustively; most are happy to find a little information that supports their belief, and reject anything that disagrees with their confirmation bias.

The chief enemy of reason is the unwillingness to consider evidence; it is rife in our society, largely because, despite years of schooling, our children are not taught how to reason dispassionately. In its simplest form, this is, ‘I’m not going to listen to your facts or your opinion.’ But, as John Stuart Mill explained in On Liberty, it is vital for us to listen even to arguments we’ve heard before that come from the mouths of fools, because conceit in our own opinions is so very strong.

Dispassionate reasoning – or critical thinking – is also rejected because some ideas are simply too uncomfortable to accept. The great film director Ingmar Bergman attacked faith in a trilogy of remarkable films in the 1950s. He was living in Sweden, a conservative Christian country, and he took quite a risk challenging strongly accepted belief.

Bergman was a nervous and unhappy man until he met his wife Ingrid (no, not that Ingrid Bergman). She brought him contentment for the first time in his life, and they lived together in marital harmony for over 20 years. After Ingrid died, Ingmar explained that he had revised his view of the afterlife, because he could not stand the thought of never seeing his beloved wife again. He knew very well that he was being irrational, but we can understand why.

Unless we stray into the belief that tens of thousands of scientists have joined in an insidious conspiracy, the evidence for climate change is now convincing. While we may not know if the Greenhouse Effect is in full swing, we do know that our industries are pouring all sorts of harmful chemicals into the environment; for the short term gain of more consumables in our consumption-addicted society, we sacrifice the health and well-being of those who follow. They will have a hard time understanding how we made such stupid mistakes. As ancestors, we may be hated and reviled, but short-term thinking is about all that most of us can manage. This is cognitive dissonance writ large.

We should explore our emotions, and learn how to express them beneficially. We should examine our intuitions, rather than pushing them aside. But if we are to survive and prosper as a species, we must temper our emotions and our intuitions with reason. In that way, we can base our decisions on evidence, and make a better, healthier and happier society.

What do you think about this article? Do you agree? Have you read Jon’s new book? Do you have a story about cognitive dissonance that you’d like to share? We’d love to hear from you!