“So ‘formal’ fallacies are when the conclusion of an argument isn’t trustworthy because of its structure or ‘form’. Informal fallacies are different. The mistake is to be found somewhere else.
Gentlemen we got twenty calls about the David Hyde peterson incident. And as you know, each call equals one billion people. Which means twenty billion people are offended by this.FCC Board Room in Family Guy
Now it’s fairly simple to put this in standard form, something like this…
1. There were twenty calls of complaint about this incident.
2. In public opinion poles, one actual complaint represents the disapproval of one million.
C. Therefore twenty billion people were offended.
Now this is only funny because we seem to know that the conclusion is crazy, but when we look closely it becomes difficult to see why. In terms of structure the two premises do seem to lead to the conclusion. So where’s the mistake? Premise 1 seems pretty good but premise 2 seems more doubtful… Now as we have already said, it doesn’t really matter how good an argument’s structure is, if the premises aren’t true we don’t need to trust the conclusion.
This probably seems like a really stupid example, but it is similar to a very persuasive informal fallacy that you need to know about for your Higher Philosophy exam. The ‘Gambler’s Fallacy’ is a name give to a mistake in reasoning that is just like the one above.