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Metamath Proof Explorer

Theorem pm2.46

Description: Theorem *2.46 of WhiteheadRussell p. 106. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm2.46 ( ¬ ( 𝜑 ∨ 𝜓 ) → ¬ 𝜓 )

Proof

Step Hyp Ref Expression
1 olc ⊢ ( 𝜓 → ( 𝜑 ∨ 𝜓 ) )
2 1 con3i ⊢ ( ¬ ( 𝜑 ∨ 𝜓 ) → ¬ 𝜓 )