Theorem frege53b 37204

Description: Lemma for frege102 (via frege92 37269). Proposition 53 of [Frege1879] p. 50. (Contributed by RP, 24-Dec-2019.) (Proof modification is discouraged.)

Assertion

Ref	Expression
frege53b	⊢ ([𝑥 / 𝑦]𝜑 → (𝑥 = 𝑧 → [𝑧 / 𝑦]𝜑))

Proof of Theorem frege53b

Step	Hyp	Ref	Expression
1		frege52b 37203	. 2 ⊢ (𝑥 = 𝑧 → ([𝑥 / 𝑦]𝜑 → [𝑧 / 𝑦]𝜑))
2		ax-frege8 37123	. 2 ⊢ ((𝑥 = 𝑧 → ([𝑥 / 𝑦]𝜑 → [𝑧 / 𝑦]𝜑)) → ([𝑥 / 𝑦]𝜑 → (𝑥 = 𝑧 → [𝑧 / 𝑦]𝜑)))
3	1, 2	ax-mp 5	1 ⊢ ([𝑥 / 𝑦]𝜑 → (𝑥 = 𝑧 → [𝑧 / 𝑦]𝜑))

Syntax hints:   → wi 4  [wsb 1867

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1713  ax-4 1728  ax-5 1827  ax-ext 2590  ax-frege8 37123  ax-frege52c 37202

This theorem depends on definitions:  df-bi 196  df-an 385  df-ex 1696  df-clab 2597  df-cleq 2603  df-clel 2606  df-sbc 3403

This theorem is referenced by:  frege55lem2b  37210