Metamath Proof Explorer


Theorem tbw-ax2

Description: The second 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-ax2 φ ψ φ

Proof

Step Hyp Ref Expression
1 ax-1 φ ψ φ