WHY IS EVIDENCE IMPORTANT? Self evidently, strong persuasive arguments are built upon solid evidence which comes from credible and convincing sources. There are many ways in which evidence can be used to suit what the arguer wants it to appear to say in support of their conclusion. Strong arguments are grounded in being honest about evidence even when it does not tell the story we want it to tell.
GOOD AND BAD REASONS FOR KNOWING Richard Dawkins, the Oxford biologist, has suggested that there are good and bad reasons for thinking we know something: (1) BAD REASONS: following tradition, believing an authority figure without questioning what they say or from revelation. (2) GOOD REASONS: from evidence of observation, experience, deduction and testing our hypotheses (hunches) in a rational fashion so that others can see how we have arrived at our conclusions BUT even on this basis there are things to be careful about.
IS THE EVIDENCE FROM A CREDIBLE SOURCE? EXAMPLE: When trying to get to the truth of a news story we should be likely to discuss the version of it carried by the BBC rather than some newspapers. EXPLANATION: Credibility refers not to truth but to the fact that most of the time a credible source is going to get things right. Arguments based on evidence from credible sources are likely to be more sound. In judging the credibility of a source factors such as: reputation, whether they were in a position to see events, whether there is a vested interest, whether the source has relevant expertise and whether it is neutral are factors to consider.
IS THE EVIDENCE RELEVANT TO THE CONCLUSION? EXAMPLE: We should stop making intrusive documentaries about the life of the Princess of Wales because the Royal Family has made it clear they are not happy about this. EXPLANATION: The views of the Royal family are used as evidence but it is irrelevant evidence because the issue should be judged on other grounds.
IS THE EVIDENCE SELECTIVE? EXAMPLE: We should not have fought Hitler in the Second World War because hundreds of thousands of deaths were the result. EXPLANATION : Weak arguments are based on evidence which is selected to support the point of view of the arguer. The evidence quoted above is valid but is only part of the picture. The war also ensured lasting democracies in Western Europe and saved many more Jews from persecution, for example.
AVOID GENERALISING FROM THE PARTICULAR OR FROM LIMITED EVIDENCE EXAMPLE: (1) In my experience men prefer to drive and not to be driven by others. (2) The French are very amorous as I found when I met a girl from Paris on holiday. EXPLANATION: Clearly here, conclusions are being made from very limited and unrepresentative evidence, a very common flaw in argument.
IS THE EVIDENCE USED IN AN INCONSISTENT WAY? EXAMPLE: My view is that people should have the freedom to smoke if they wish. The research evidence produced by ASH (Action on Smoking and Health) should be ignored because they are do-gooders. Research by the tobacco industry has been much better conducted. EXPLANATION: The approach to the evidence here is inconsistent because different standards are applied to the point of view with which the arguer disagrees. All evidence should be judged on the same terms: whether it is sound or not.
NEUTRALISING THE MEANING OF LANGUAGE EXAMPLE: (1) Collateral damage Killing civilians (2) Human remains pouches Body bags (3) Strategic withdrawal Defeat (4) Job rescheduling Sacked EXPLANATION: This is doublespeak, using emotionally neutral terms to describe emotionally charged or controversial issues in order to make the evidence seem less significant or more acceptable. Governments and armed forces often do this.