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Monday, November 30, 2020

Bad arguments #7 - equating correlation with causation


'In my last Maths test I got 90%, my best ever result. I also wore red socks that day. I’ve got another Maths test tomorrow. How should I ensure I get 90% again? Obvious! Forget revision - just wear red socks!'

What’s wrong with that argument?

It’s equating correlation with causation, that’s what.

Equating, correlation and causation are long words, and you may not know what they mean (or maybe you do).

In case you don’t:

  • Correlation means one thing following another.
  • Causation means one thing causing another.
  • Equating means assuming two things are the same.

This bad argument can be summed up thus:

The fact that A is followed by, or happens at the same time as, B does not prove that B is caused by A.

Of course, most people aren’t stupid enough to think that Maths test results depend on sock colour. But you do see variations on this bad argument used in debates.

For example, in a debate on the motion ‘This house would ban violent computer games’, the proposition argue:

‘Violent computer games have never been more popular. At the same time, levels of knife crime amongst young people have never been higher. We need to ban these games now to keep our children safe!’

Knife crime is indisputably a bad thing. Its growth may be happening at the same time as a growth in downloads of violent computer games. But that doesn’t, in itself, prove that violent computer games cause knife crime. To do that, you would have to find specific examples of acts of violence that were directly inspired by computer games.

So what should you say to rebut this? You can start by pointing out the logical fallacy:

‘Horrific though knife crime is, you have not provided any evidence that it is connected with the use of violent computer games.’

Or, you can turn the connection between the two factors round so that the correlation works in your favour:

‘Millions of young people play violent computer games every day, and only a tiny minority engage in acts of violence; this is surely compelling evidence that playing these games is harmless.’

To sum up:

  •  One thing being followed by, or happening at the same time as, another thing does not mean that the second thing is caused by the first.
  • If your opponent tries to use this argument, expose the lack of connection between the two factors.

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