Theorem pm4.24

Description: Theorem *4.24 of WhiteheadRussell p. 117. (Contributed by NM, 11-May-1993)

	Ref	Expression
Assertion	pm4.24	$$⊢\phi \leftrightarrow \left(\phi \wedge \phi \right)$$

Proof

Step	Hyp	Ref	Expression
1		id	$$⊢\phi \to \phi$$
2	1	pm4.71i	$$⊢\phi \leftrightarrow \left(\phi \wedge \phi \right)$$