Theorem pm3.14

Description: Theorem *3.14 of WhiteheadRussell p. 111. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm3.14	⊢ ( ( ¬ 𝜑 ∨ ¬ 𝜓 ) → ¬ ( 𝜑 ∧ 𝜓 ) )

Proof

Step	Hyp	Ref	Expression
1		pm3.1	⊢ ( ( 𝜑 ∧ 𝜓 ) → ¬ ( ¬ 𝜑 ∨ ¬ 𝜓 ) )
2	1	con2i	⊢ ( ( ¬ 𝜑 ∨ ¬ 𝜓 ) → ¬ ( 𝜑 ∧ 𝜓 ) )