Theorem cbv1h 2439

Description: Rule used to change bound variables, using implicit substitution. Usage of this theorem is discouraged because it depends on ax-13 2406. (Contributed by NM, 11-May-1993.) (Proof shortened by Wolf Lammen, 13-May-2018.) (New usage is discouraged.)

Hypotheses

Ref	Expression
cbv1h.1	⊢ (𝜑 → (𝜓 → ∀𝑦𝜓))
cbv1h.2	⊢ (𝜑 → (𝜒 → ∀𝑥𝜒))
cbv1h.3	⊢ (𝜑 → (𝑥 = 𝑦 → (𝜓 → 𝜒)))

Assertion

Ref	Expression
cbv1h	⊢ (∀𝑥∀𝑦𝜑 → (∀𝑥𝜓 → ∀𝑦𝜒))

Proof of Theorem cbv1h

Step	Hyp	Ref	Expression
1		nfa1 2189	. 2 ⊢ Ⅎ𝑥∀𝑥∀𝑦𝜑
2		nfa2 2213	. 2 ⊢ Ⅎ𝑦∀𝑥∀𝑦𝜑
3		2sp 2225	. . . 4 ⊢ (∀𝑥∀𝑦𝜑 → 𝜑)
4		cbv1h.1	. . . 4 ⊢ (𝜑 → (𝜓 → ∀𝑦𝜓))
5	3, 4	syl 18	. . 3 ⊢ (∀𝑥∀𝑦𝜑 → (𝜓 → ∀𝑦𝜓))
6	2, 5	nf5d 2321	. 2 ⊢ (∀𝑥∀𝑦𝜑 → Ⅎ𝑦𝜓)
7		cbv1h.2	. . . 4 ⊢ (𝜑 → (𝜒 → ∀𝑥𝜒))
8	3, 7	syl 18	. . 3 ⊢ (∀𝑥∀𝑦𝜑 → (𝜒 → ∀𝑥𝜒))
9	1, 8	nf5d 2321	. 2 ⊢ (∀𝑥∀𝑦𝜑 → Ⅎ𝑥𝜒)
10		cbv1h.3	. . 3 ⊢ (𝜑 → (𝑥 = 𝑦 → (𝜓 → 𝜒)))
11	3, 10	syl 18	. 2 ⊢ (∀𝑥∀𝑦𝜑 → (𝑥 = 𝑦 → (𝜓 → 𝜒)))
12	1, 2, 6, 9, 11	cbv1 2436	1 ⊢ (∀𝑥∀𝑦𝜑 → (∀𝑥𝜓 → ∀𝑦𝜒))

This proof depends on syntax axioms:   → wi 4  ∀wal 1568

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041  ax-10 2179  ax-11 2195  ax-12 2216  ax-13 2406

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-ex 1813  df-nf 1817

This theorem is used by:  cbv2h  2440