Theorem pm2.32

Description: Theorem *2.32 of WhiteheadRussell p. 105. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm2.32	$$⊢\left(\left(\phi \vee \psi \right)\vee \chi \right)\to \left(\phi \vee \left(\psi \vee \chi \right)\right)$$

Proof

Step	Hyp	Ref	Expression
1		orass	$$⊢\left(\left(\phi \vee \psi \right)\vee \chi \right)\leftrightarrow \left(\phi \vee \left(\psi \vee \chi \right)\right)$$
2	1	biimpi	$$⊢\left(\left(\phi \vee \psi \right)\vee \chi \right)\to \left(\phi \vee \left(\psi \vee \chi \right)\right)$$