[F04] Insufficiency

Module: Fallacies and biases

Quote of the page

I think and think for months and years. Ninety-nine times, the conclusion is false. The hundredth time I am right.

- Albert Einstein

Help us promote
critical thinking!

Popular pages

  1. What is critical thinking?
  2. What is logic?
  3. Hardest logic puzzle ever
  4. Free miniguide
  5. What is an argument?
  6. Knights and knaves puzzles
  7. Logic puzzles
  8. What is a good argument?
  9. Improving critical thinking
  10. Analogical arguments

Fallacies of insufficiency are cases where insufficient evidence is provided in support of a claim. Probably most common fallacies fall within this category. Here are a few popular types:

Limited sampling

  • Momofuku Ando, the inventor of instant noodles, died at the age of 96. He said he ate instant noodles everyday. So instant noodles cannot be bad for your health.
  • A black cat crossed my path this morning, and I got into a traffic accident this afternoon. Black cats are really unlucky.

In both cases the observations are relevant to the conclusion, but a lot more data is needed to support the conclusion, e.g. Studies show that many other people who eat instant noodles live longer, and those who encounter black cats are more likely to suffer from accidents.

Appeal to ignorance

  • We have no evidence showing that he is innocent. So he must be guilty.

If someone is guilty, it would indeed be hard to find evidence showing that he is innocent. But perhaps there is no evidence to point either way, so lack of evidence is not enough to prove guilt.

Naturalistic fallacy

  • Many children enjoy playing video games, so we should not stop them from playing.

Many naturalistic fallacies are examples of fallacy of insufficiency. Empirical facts by themselves are not sufficient for normative conclusions, even if they are relevant.

There are many other kinds of fallacy of insufficiency. See if you can identify some of them.

previous tutorial next tutorial


© 2004-2024 Joe Lau & Jonathan Chan