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Axiom ax-frege58a 36983
Description: If 𝑥𝜑 is affirmed, [𝑦 / 𝑥]𝜑 cannot be denied. Identical to stdpc4 2341. Axiom 58 of [Frege1879] p. 51. (Contributed by RP, 28-Mar-2020.) (New usage is discouraged.)
Assertion
Ref Expression
ax-frege58a ((𝜓𝜒) → if-(𝜑, 𝜓, 𝜒))

Detailed syntax breakdown of Axiom ax-frege58a
StepHypRef Expression
1 wps . . 3 wff 𝜓
2 wch . . 3 wff 𝜒
31, 2wa 383 . 2 wff (𝜓𝜒)
4 wph . . 3 wff 𝜑
54, 1, 2wif 1006 . 2 wff if-(𝜑, 𝜓, 𝜒)
63, 5wi 4 1 wff ((𝜓𝜒) → if-(𝜑, 𝜓, 𝜒))
Colors of variables: wff setvar class
This axiom is referenced by:  frege58acor  36984  frege61a  36987  frege67a  36993
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