Informal proofs are the type of proof typically encountered in published mathematics.

An informal proof will be provided here.

Resolution for surfaces over the complex numbers was given informal proofs by , and .

An informal proof in the mathematics literature, by contrast, requires weeks of peer review to be checked, and may still contain errors.

Click to show an informal proof.

Although each informal proof can, in theory, be converted into a formal proof, this is rarely done in practice.

An informal proof follows.

The informal proofs of everyday mathematical practice are unlike the formal proofs of proof theory.

Because of their use of natural language, the standards of rigor for informal proofs will depend on the audience of the proof.

The first is an informal proof, a rigorous natural-language expression that is intended to convince the audience of the truth of a theorem.

The distinction between formal and informal proofs has led to much examination of current and historical mathematical practice, quasi-empiricism in mathematics, and so-called folk mathematics (in both senses of that term).

Graham Priest (1984, 2006) argues that replacing the notion of formal proof in Gödel's theorem with the usual notion of informal proof can be used to show that naive mathematics is inconsistent, and uses this as evidence for dialetheism.