# Rule of Idempotence/Conjunction

## Theorem

### Formulation 1

$p \dashv \vdash p \land p$

### Formulation 2

$\vdash p \iff \paren {p \land p}$

Its abbreviation in a tableau proof is $\textrm{Idemp}$.

## Also known as

This rule is also known as the law of tautology for logical multiplication (or conjunction).