Theorem retbwax3 1488

Description: tbw-ax3 1467 rederived from merco1 1478. (Contributed by Anthony Hart, 17-Sep-2011.) (Proof modification is discouraged.) (New usage is discouraged.)

Assertion

Ref	Expression
retbwax3	⊢ (((φ → ψ) → φ) → φ)

Proof of Theorem retbwax3

Step	Hyp	Ref	Expression
1		retbwax2 1481	. 2 ⊢ (φ → (φ → φ))
2		merco1lem7 1487	. 2 ⊢ ((φ → (φ → φ)) → (((φ → ψ) → φ) → φ))
3	1, 2	ax-mp 5	1 ⊢ (((φ → ψ) → φ) → φ)

Syntax hints:   → wi 4

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

This theorem depends on definitions:  df-bi 177  df-tru 1319  df-fal 1320

This theorem is referenced by: (None)