Theorem impi 124

Description: An importation inference.

Hypothesis

Ref	Expression
impi.1	⊢ (φ → (ψ → χ))

Assertion

Ref	Expression
impi	⊢ (¬ (φ → ¬ ψ) → χ)

Proof of Theorem impi

Step	Hyp	Ref	Expression
1		impi.1	. 2 ⊢ (φ → (ψ → χ))
2		impt 122	. 2 ⊢ ((φ → (ψ → χ)) → (¬ (φ → ¬ ψ) → χ))
3	1, 2	ax-mp 6	1 ⊢ (¬ (φ → ¬ ψ) → χ)

Syntax hints:  ¬ wn 1   → wi 2

This theorem is referenced by:  bii 140  imp 277  meredith 644

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

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