Theorem pm2.521g

Description: A general instance of Theorem *2.521 of WhiteheadRussell p. 107. (Contributed by BJ, 28-Oct-2023)

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

Proof

Step	Hyp	Ref	Expression
1		conax1	$$⊢\neg \left(\phi \to \psi \right)\to \neg \psi$$
2	1	pm2.21d	$$⊢\neg \left(\phi \to \psi \right)\to \left(\psi \to \chi \right)$$