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