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Axiom ax-frege54a 40561
Description: Reflexive equality of wffs. The content of 𝜑 is identical with the content of 𝜑. Part of Axiom 54 of [Frege1879] p. 50. Identical to biid 264. (Contributed by RP, 24-Dec-2019.) (New usage is discouraged.)
Ref Expression
ax-frege54a (𝜑𝜑)

Detailed syntax breakdown of Axiom ax-frege54a
StepHypRef Expression
1 wph . 2 wff 𝜑
21, 1wb 209 1 wff (𝜑𝜑)
Colors of variables: wff setvar class
This axiom is referenced by:  frege54cor1a  40563
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