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Axiom ax-frege58b 37677
Description: If 𝑥𝜑 is affirmed, [𝑦 / 𝑥]𝜑 cannot be denied. Identical to stdpc4 2352. Axiom 58 of [Frege1879] p. 51. (Contributed by RP, 28-Mar-2020.) (New usage is discouraged.)
Assertion
Ref Expression
ax-frege58b (∀𝑥𝜑 → [𝑦 / 𝑥]𝜑)

Detailed syntax breakdown of Axiom ax-frege58b
StepHypRef Expression
1 wph . . 3 wff 𝜑
2 vx . . 3 setvar 𝑥
31, 2wal 1478 . 2 wff 𝑥𝜑
4 vy . . 3 setvar 𝑦
51, 2, 4wsb 1877 . 2 wff [𝑦 / 𝑥]𝜑
63, 5wi 4 1 wff (∀𝑥𝜑 → [𝑦 / 𝑥]𝜑)
Colors of variables: wff setvar class
This axiom is referenced by:  frege58bid  37678  frege58bcor  37679  frege60b  37681  frege61b  37682  frege67b  37688  frege58c  37697
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