Theorem pm2.21ni 92

Description: Inference related to pm2.21 71.

Hypothesis

Ref	Expression
pm2.21ni.1	⊢ φ

Assertion

Ref	Expression
pm2.21ni	⊢ (¬ φ → ψ)

Proof of Theorem pm2.21ni

Step	Hyp	Ref	Expression
1		pm2.21ni.1	. . 3 ⊢ φ
2	1	a1i 7	. 2 ⊢ (¬ ψ → φ)
3	2	con1i 88	1 ⊢ (¬ φ → ψ)

Syntax hints:  ¬ wn 1   → wi 2

This theorem is referenced by:  niabn 566  snsspr 1853  nneo 4719

This theorem was proved from axioms:  ax-1 3  ax-2 4  ax-3 5  ax-mp 6

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