Theorem pm2.521g2

Description: A general instance of Theorem *2.521 of WhiteheadRussell p. 107. (Contributed by NM, 3-Jan-2005) (Proof shortened by Wolf Lammen, 8-Oct-2012)

	Ref	Expression
Assertion	pm2.521g2	$$⊢\neg \left(\phi \to \psi \right)\to \left(\chi \to \phi \right)$$

Proof

Step	Hyp	Ref	Expression
1		simplim	$$⊢\neg \left(\phi \to \psi \right)\to \phi$$
2	1	a1d	$$⊢\neg \left(\phi \to \psi \right)\to \left(\chi \to \phi \right)$$