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
|- ( ( ( ph -> ps ) -> ph ) -> ph )

Proof

Step Hyp Ref Expression
1 peirce
 |-  ( ( ( ph -> ps ) -> ph ) -> ph )