Theorem pm1.4

Description: Axiom *1.4 of WhiteheadRussell p. 96. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm1.4	⊢ ( ( 𝜑 ∨ 𝜓 ) → ( 𝜓 ∨ 𝜑 ) )

Proof

Step	Hyp	Ref	Expression
1		olc	⊢ ( 𝜑 → ( 𝜓 ∨ 𝜑 ) )
2		orc	⊢ ( 𝜓 → ( 𝜓 ∨ 𝜑 ) )
3	1 2	jaoi	⊢ ( ( 𝜑 ∨ 𝜓 ) → ( 𝜓 ∨ 𝜑 ) )