Counterexample

A counter-example is in mathematics or philosophy, especially in logic or constructed an empirical facts which refute a particular hypothesis. Since Karl Popper's falsifiability requirement for valid today only such statements as scientific, to which counterexamples are possible.

In mathematics there is a large field, which is based on propositional logic. In this logic, a statement is true or false. Statements concerning a set of objects is false if it is false for an object. This object is then called a counterexample.

Examples

• Gettiers counter-examples to the claim that knowledge is " justified true belief ".

• Statement: All natural numbers are. Counter-example: the number one. The number one is a natural number and odd. So the statement is refuted.