Theorem cbv2 2404

Description: Rule used to change bound variables, using implicit substitution. Usage of this theorem is discouraged because it depends on ax-13 2373. See cbv2w 2337 with disjoint variable conditions, not depending on ax-13 2373. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 3-Oct-2016.) Format hypotheses to common style, avoid ax-10 2140. (Revised by Wolf Lammen, 10-Sep-2023.) (New usage is discouraged.)

Hypotheses

Ref	Expression
cbv2.1	⊢ Ⅎ𝑥𝜑
cbv2.2	⊢ Ⅎ𝑦𝜑
cbv2.3	⊢ (𝜑 → Ⅎ𝑦𝜓)
cbv2.4	⊢ (𝜑 → Ⅎ𝑥𝜒)
cbv2.5	⊢ (𝜑 → (𝑥 = 𝑦 → (𝜓 ↔ 𝜒)))

Assertion

Ref	Expression
cbv2	⊢ (𝜑 → (∀𝑥𝜓 ↔ ∀𝑦𝜒))

Proof of Theorem cbv2

Step	Hyp	Ref	Expression
1		cbv2.1	. . 3 ⊢ Ⅎ𝑥𝜑
2		cbv2.2	. . 3 ⊢ Ⅎ𝑦𝜑
3		cbv2.3	. . 3 ⊢ (𝜑 → Ⅎ𝑦𝜓)
4		cbv2.4	. . 3 ⊢ (𝜑 → Ⅎ𝑥𝜒)
5		cbv2.5	. . . 4 ⊢ (𝜑 → (𝑥 = 𝑦 → (𝜓 ↔ 𝜒)))
6		biimp 214	. . . 4 ⊢ ((𝜓 ↔ 𝜒) → (𝜓 → 𝜒))
7	5, 6	syl6 35	. . 3 ⊢ (𝜑 → (𝑥 = 𝑦 → (𝜓 → 𝜒)))
8	1, 2, 3, 4, 7	cbv1 2403	. 2 ⊢ (𝜑 → (∀𝑥𝜓 → ∀𝑦𝜒))
9		equcomi 2023	. . . 4 ⊢ (𝑦 = 𝑥 → 𝑥 = 𝑦)
10		biimpr 219	. . . 4 ⊢ ((𝜓 ↔ 𝜒) → (𝜒 → 𝜓))
11	9, 5, 10	syl56 36	. . 3 ⊢ (𝜑 → (𝑦 = 𝑥 → (𝜒 → 𝜓)))
12	2, 1, 4, 3, 11	cbv1 2403	. 2 ⊢ (𝜑 → (∀𝑦𝜒 → ∀𝑥𝜓))
13	8, 12	impbid 211	1 ⊢ (𝜑 → (∀𝑥𝜓 ↔ ∀𝑦𝜒))

Syntax hints:   → wi 4   ↔ wb 205  ∀wal 1539  Ⅎwnf 1789

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1801  ax-4 1815  ax-5 1916  ax-6 1974  ax-7 2014  ax-11 2157  ax-12 2174  ax-13 2373

This theorem depends on definitions:  df-bi 206  df-an 396  df-or 844  df-ex 1786  df-nf 1790

This theorem is referenced by:  cbvald  2408  cbval2  2412  sb9  2524  wl-cbvalnaed  35670  wl-sb8t  35686