Description: The second of three axioms in the Tarski-Bernays axiom system. (Contributed by Anthony Hart, 16-Aug-2011) (Proof modification is discouraged.) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | tb-ax2 | ⊢ ( 𝜑 → ( 𝜓 → 𝜑 ) ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ax-1 | ⊢ ( 𝜑 → ( 𝜓 → 𝜑 ) ) |