Theorem retbwax4

Description: tbw-ax4 rederived from merco1 . (Contributed by Anthony Hart, 17-Sep-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	retbwax4	⊢ ( ⊥ → 𝜑 )

Proof

Step	Hyp	Ref	Expression
1		merco1lem1	⊢ ( 𝜑 → ( ⊥ → 𝜑 ) )
2		merco1lem1	⊢ ( ( 𝜑 → ( ⊥ → 𝜑 ) ) → ( ⊥ → 𝜑 ) )
3	1 2	ax-mp	⊢ ( ⊥ → 𝜑 )