This is an inofficial mirror of http://metamath.tirix.org for personal testing of a visualizer extension only.

Metamath Proof Explorer

Theorem tbw-ax3

Description: The third of four axioms in the Tarski-Bernays-Wajsberg system. (Contributed by Anthony Hart, 13-Aug-2011) (Proof modification is discouraged.) (New usage is discouraged.)

		Ref	Expression
	Assertion	tbw-ax3	$⊢ ((φ \to ψ) \to φ) \to φ$

Proof

Step	Hyp	Ref	Expression
1		peirce	$⊢ ((φ \to ψ) \to φ) \to φ$