Proof by example

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Proof by example (also known as inappropriate generalisation) is a logical fallacy whereby one or more examples are claimed as "proof" for a more general statement.

This fallacy has the following argument form:

I know that x X has the property P.

Therefore, all other elements of X have the property P.

The following example demonstrates why this is a logical fallacy:

I've seen a person shoot someone.

Therefore, all people are murderers.

That argument is obviously flawed, but arguments of the same form can sometimes seem superficially convincing, as in the following example:

I've seen John's brother steal something. John's family must be thieves.

[edit] See also

• Modus ponens
• Affirming the consequent

v • d • e Formal fallacies Argument from fallacy • Fallacy of modal logic • Masked man fallacy • Appeal to probability • Bare assertion fallacy Fallacy of propositional logic: Affirming a disjunct • Affirming the consequent • False dilemma • Denying the antecedent Fallacy of quantificational logic: Existential fallacy • Illicit Conversion • Proof by example • Quantifier shift Syllogistic fallacy: Affirmative conclusion from a negative premise • Exclusive premises • Necessity • Four-term Fallacy • Illicit major • Illicit minor • Undistributed middle Other types of fallacy