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Theorem frege58bid 39035
Description: If 𝑥𝜑 is affirmed, 𝜑 cannot be denied. Identical to sp 2224. See ax-frege58b 39034 and frege58c 39054 for versions which more closely track the original. Axiom 58 of [Frege1879] p. 51. (Contributed by RP, 28-Mar-2020.) (Proof modification is discouraged.)
Assertion
Ref Expression
frege58bid (∀𝑥𝜑𝜑)

Proof of Theorem frege58bid
StepHypRef Expression
1 ax-frege58b 39034 . 2 (∀𝑥𝜑 → [𝑥 / 𝑥]𝜑)
2 sbid 2289 . . 3 ([𝑥 / 𝑥]𝜑𝜑)
32biimpi 208 . 2 ([𝑥 / 𝑥]𝜑𝜑)
41, 3syl 17 1 (∀𝑥𝜑𝜑)
Colors of variables: wff setvar class
Syntax hints:  wi 4  wal 1654  [wsb 2067
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1894  ax-4 1908  ax-5 2009  ax-6 2075  ax-7 2112  ax-12 2220  ax-frege58b 39034
This theorem depends on definitions:  df-bi 199  df-an 387  df-ex 1879  df-sb 2068
This theorem is referenced by: (None)
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