Editor's Note: This entry is part 2 of 3 in the series Cognitive Dissonance, or Evidence Versus Opinion

Evidence is specific, where emotional responses tend to generalise. I reject both criticism and praise that are not specific. It is impossible to truly benefit from a generalisation. If someone accuses me of a bad behaviour, I want at least one example. Many people find this annoying, because although they are emotionally sure of some defect, they often cannot find any evidence: they feel annoyed and want to express it, but the annoyance may well have more to do with their feelings than with anything we’ve either said or done. Generalised criticism is the province of the gaslighting predator, and should always be treated with caution.

We can separate evidence from opinion, but first we need to have a good idea of what ‘evidence’ is. Trained scientists may skip the next few paragraphs.

Science is not a belief system – unlike religion, politics, or economics – but a method of enquiry. Science is based upon observation and experiment. Ideas evolve through different stages in the scientific method: first comes hypothesis, which is the original idea. So, Newton perhaps thought that things fall down, which would be a hypothesis.

Next comes experiment, where a hypothesis is tested: Newton might drop some apples and see which way they went – up, down or sideways. The conditions of the experiment mean that it must be able to both prove and disprove the hypothesis, so if the apples fell up or stayed put, that would be disproof, or ‘falsification’, if they all fell down, that is proof or “validation”.

The experiment must be replicated by an independent team, which includes no one from the original group. If this replication is successful, then the hypothesis is elevated to the status of a theory – which is to say, a hypothesis with confirming information (the word “theory” is much misunderstood by Creationists).

Once a theory has been replicated often enough, a law has been discovered, so Newton went from the idea of gravity – a hypothesis – through to experiments (okay, I know we’re heading towards the inverse square law, but let’s not get too complicated here!) and on to a theory. Given enough replication, that theory is seen as a law – something that predicts action: if I drop an apple, or anything else, in a gravitational field, it will fall downwards.

Unlike religion – where truths are considered absolute and unchanging – with science, the jury will always be out: any scientific idea can be challenged using the scientific method of observation and experiment. Indeed, dearly held beliefs have been overturned at times, and some scientific “truths” have later proved to be unscientific.

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! 

Series NavigationCognitive Dissonance, or Evidence Versus Opinion, Part OneCognitive Dissonance, or Evidence Versus Opinion, Part Three