**Proof by example** (also known as **inappropriate generalization**) is a logical fallacy whereby one or more examples are claimed as “proof” for a more general statement.^{
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This fallacy has the following structure, and argument form:

Structure:

- I know that X is such.
- Therefore, anything related to X is also such.

Argument form:

- I know that x, which is a member of group 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 dead.
- Therefore, all people are murderers.

The flaw in this argument is very evident, but arguments of the same form can sometimes seem somewhat convincing, as in the following example:

- I’ve seen Gypsies steal. So, Gypsies must be thieves.

However, argument by example is valid when it leads from a singular premise to an *existential* conclusion. For example:

- Socrates is wise.
- Therefore, someone is wise.

(or)

- I’ve seen a person steal.
- Therefore, people can steal.