Metamath Proof Explorer


Theorem tb-ax3

Description: The third of three axioms in the Tarski-Bernays axiom system.

This axiom, along with ax-mp , tb-ax1 , and tb-ax2 , can be used to derive any theorem or rule that uses only -> . (Contributed by Anthony Hart, 16-Aug-2011) (Proof modification is discouraged.) (New usage is discouraged.)

Ref Expression
Assertion tb-ax3 ( ( ( 𝜑𝜓 ) → 𝜑 ) → 𝜑 )

Proof

Step Hyp Ref Expression
1 peirce ( ( ( 𝜑𝜓 ) → 𝜑 ) → 𝜑 )