Theorem sbt 2071

Description: A substitution into a theorem yields a theorem. See sbtALT 2074 for a shorter proof requiring more axioms. See chvar 2397 and chvarv 2398 for versions using implicit substitution. (Contributed by NM, 21-Jan-2004.) (Proof shortened by Andrew Salmon, 25-May-2011.) (Proof shortened by Wolf Lammen, 20-Jul-2018.) Revise df-sb 2068. (Revised by Steven Nguyen, 6-Jul-2023.) Revise df-sb 2068 again. (Revised by Wolf Lammen, 4-Feb-2026.)

Hypothesis

Ref	Expression
sbt.1	⊢ 𝜑

Assertion

Ref	Expression
sbt	⊢ [𝑡 / 𝑥]𝜑

Proof of Theorem sbt

Dummy variables 𝑦 𝑧 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		sbt.1	. . 3 ⊢ 𝜑
2	1	sbtlem 2070	. 2 ⊢ ∀𝑦(𝑦 = 𝑡 → ∀𝑥(𝑥 = 𝑦 → 𝜑))
3	1	sbtlem 2070	. . . 4 ⊢ ∀𝑧(𝑧 = 𝑡 → ∀𝑥(𝑥 = 𝑧 → 𝜑))
4	2, 3	2th 264	. . 3 ⊢ (∀𝑦(𝑦 = 𝑡 → ∀𝑥(𝑥 = 𝑦 → 𝜑)) ↔ ∀𝑧(𝑧 = 𝑡 → ∀𝑥(𝑥 = 𝑧 → 𝜑)))
5	4	df-sb 2068	. 2 ⊢ ([𝑡 / 𝑥]𝜑 ↔ ∀𝑦(𝑦 = 𝑡 → ∀𝑥(𝑥 = 𝑦 → 𝜑)))
6	2, 5	mpbir 231	1 ⊢ [𝑡 / 𝑥]𝜑

Syntax hints:   → wi 4  ∀wal 1539  [wsb 2067

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1796

This theorem depends on definitions:  df-bi 207  df-sb 2068

This theorem is referenced by:  sbtru  2072  sbimi  2079  vexw  2718  iscatd2  17602  iuninc  32584  suppss2f  32665  esumpfinvalf  34182  sbtT  44750  2sb5ndVD  45092  2sb5ndALT  45114  icht  47640