Theorem pm2.27

Description: This theorem, sometimes called "Assertion" or "Pon" (for "ponens"), can be thought of as a closed form of modus ponens ax-mp . Theorem *2.27 of WhiteheadRussell p. 104. (Contributed by NM, 15-Jul-1993)

	Ref	Expression
Assertion	pm2.27	$$⊢\phi \to \left(\left(\phi \to \psi \right)\to \psi \right)$$

Proof

Step	Hyp	Ref	Expression
1		id	$$⊢\left(\phi \to \psi \right)\to \left(\phi \to \psi \right)$$
2	1	com12	$$⊢\phi \to \left(\left(\phi \to \psi \right)\to \psi \right)$$