- Anecdotal evidence is basically saying "X happened to me/someone I know/someone I heard about" in a discussion and/or argument. If it's true that X happened to this person, it proves only that X is not impossible. It most certainly does not establish that X has ever happened more than once, or that X is common or pervasive - and that's what this fallacy about. The Anecdotal Fallacy is using anecdotes instead of actual statistics and making general rules and grand claims off them, accurate picture of the reality of the matter be damned. Crops up often in heated arguments and amidst Hasty Generalisations, whereby an anecdote is not just used to illustrate or critique a general rule but as 'proof'note in itself. As they say, "The plural of 'anecdote' is not 'data'".
"According to statistics, smoking causes you to die young. But my Grandmother Sally smoked like a chimney and lived until she was 95, so clearly the statistics are wrong."
As a rebuttal, one might simply point out that they met a man on the way home who said that anecdotal evidence doesn't prove anything.
- A belief that some event was caused by the supernatural usually falls into this category. For example, if you asked the Abrahamic-Monotheistic God to heal your grandma, and she got better, that wouldn't prove God did it. While such an episode might be powerful to the individual, it is only a data point and does not prove anything. A hundred other people might ask for the same thing and get dead grandmas.
- Even better, people on both sides of the debate will pull this off. If your grandma didn't make a recovery then God doesn't exist, but you dismiss any cases where she did as 'lucky', while believers will take any recovery as unassailable proof of God, and any case without a recovery was God's will.
- Another instance of this is what is sometimes called "argument from mere analogy" — the mistaken belief that because analogy is often used to illustrate proof, therefore analogy is proof.
- One example is used by those who believe that time is the fourth dimension, and that therefore no spatial fourth dimension is possible.note They "prove" this by arguing that a being who is capable of time travel, and who finds itself trapped in a hollow cube, can escape by travelling to a time before the cube existed, or after it ceased to exist. Apart from the fact of being stolen almost verbatim from Isaac Asimov's short story "Gimmicks Three", if this "proves" anything, all it proves is that if time is a dimension in the sense that time travel is possible, and there exists a being as described, then the escape described is possible; it doesn't prove that time is such a dimension, much less that it must be the sole possibility.
Looks like this fallacy but isn't:
- When the anecdote is offered as a data point, not proof.
- When a lot of anecdotes have been collected, and they are consistent. This isn't a fallacy; it's inductive reasoning. Refusing to come to a conclusion based on repeated anecdotes is the fallacy of slothful induction, also known as poor pattern recognition. When Lucy pulls the football away from Charlie Brown again and again, but he keeps trusting her, he isn't avoiding the anecdotal fallacy; he's being a fool.
- When the anecdote is used to counter a universal claim as a counter-example; using the example above, claiming that grandma is a long-lived heavy smoker with no health problems doesn't prove that smoking is healthy, but it does disprove the claim that "All smokers get cancer and die young". A universal claim (All A are B) is disproven by the existence of even one case where A is not B.