Theorem pm2.18dOLD 130

Description: Obsolete version of pm2.18d 127 as of 17-Nov-2023. (Contributed by FL, 12-Jul-2009.) (Proof shortened by Andrew Salmon, 7-May-2011.) (Proof modification is discouraged.) (New usage is discouraged.)

Hypothesis

Ref	Expression
pm2.18dOLD.1	⊢ (𝜑 → (¬ 𝜓 → 𝜓))

Assertion

Ref	Expression
pm2.18dOLD	⊢ (𝜑 → 𝜓)

Proof of Theorem pm2.18dOLD

Step	Hyp	Ref	Expression
1		pm2.18dOLD.1	. 2 ⊢ (𝜑 → (¬ 𝜓 → 𝜓))
2		pm2.18OLD 129	. 2 ⊢ ((¬ 𝜓 → 𝜓) → 𝜓)
3	1, 2	syl 17	1 ⊢ (𝜑 → 𝜓)

Syntax hints:  ¬ wn 3   → wi 4

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem is referenced by: (None)