Theorem pm2.3

Description: Theorem *2.3 of WhiteheadRussell p. 104. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm2.3	⊢ ( ( 𝜑 ∨ ( 𝜓 ∨ 𝜒 ) ) → ( 𝜑 ∨ ( 𝜒 ∨ 𝜓 ) ) )

Proof

Step	Hyp	Ref	Expression
1		pm1.4	⊢ ( ( 𝜓 ∨ 𝜒 ) → ( 𝜒 ∨ 𝜓 ) )
2	1	orim2i	⊢ ( ( 𝜑 ∨ ( 𝜓 ∨ 𝜒 ) ) → ( 𝜑 ∨ ( 𝜒 ∨ 𝜓 ) ) )