Axiom ax-frege58a

Description: If A. x ph is affirmed, [ y / x ] ph cannot be denied. Identical to stdpc4 . Axiom 58 of Frege1879 p. 51. (Contributed by RP, 28-Mar-2020) (New usage is discouraged.)

	Ref	Expression
Assertion	ax-frege58a	$$⊢\left(\psi \wedge \chi \right)\to if-\left(\phi ,\psi ,\chi \right)$$

Detailed syntax breakdown

Step	Hyp	Ref	Expression
0		wps	$$wff\psi$$
1		wch	$$wff\chi$$
2	0 1	wa	$$wff\left(\psi \wedge \chi \right)$$
3		wph	$$wff\phi$$
4	3 0 1	wif	$$wffif-\left(\phi ,\psi ,\chi \right)$$
5	2 4	wi	$$wff\left(\left(\psi \wedge \chi \right)\to if-\left(\phi ,\psi ,\chi \right)\right)$$