# Peirce's law

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## Definition of the noun Peirce's Law

What does Peirce's Law mean as a name of something?

**noun**

- [
*logic*] The classically valid but intuitionistically non-valid formula $((P\; \backslash to\; Q)\; \backslash to\; P)\; \backslash to\; P$ of propositional calculus, which can be used as an substitute for the law of excluded middle in implicational propositional calculus.

## Explanation

**Peirce's law**: In logic, Peirce's law is named after the philosopher and logician Charles Sanders Peirce. It was taken as an axiom in his first axiomatisation of propositional logic. It can be thought of as the law of excluded middle written in a form that involves only one sort of connective, namely implication.

- also known as 皮尔士定律

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**Peirce's law Meaning**

Video shows what Peirce's law means. The classically valid but intuitionistically non-valid formula ((P \to Q) \to P) \to P of propositional calculus, which can be ...

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