Theorem axregnd 9741

Description: A version of the Axiom of Regularity with no distinct variable conditions. (Contributed by NM, 3-Jan-2002.) (Proof shortened by Wolf Lammen, 18-Aug-2019.)

Assertion

Ref	Expression
axregnd	⊢ (𝑥 ∈ 𝑦 → ∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦)))

Proof of Theorem axregnd

Dummy variable 𝑤 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		axregndlem2 9740	. . . 4 ⊢ (𝑥 ∈ 𝑦 → ∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑤(𝑤 ∈ 𝑥 → ¬ 𝑤 ∈ 𝑦)))
2		nfnae 2455	. . . . . 6 ⊢ Ⅎ𝑥 ¬ ∀𝑧 𝑧 = 𝑥
3		nfnae 2455	. . . . . 6 ⊢ Ⅎ𝑥 ¬ ∀𝑧 𝑧 = 𝑦
4	2, 3	nfan 2002	. . . . 5 ⊢ Ⅎ𝑥(¬ ∀𝑧 𝑧 = 𝑥 ∧ ¬ ∀𝑧 𝑧 = 𝑦)
5		nfnae 2455	. . . . . . . 8 ⊢ Ⅎ𝑧 ¬ ∀𝑧 𝑧 = 𝑥
6		nfnae 2455	. . . . . . . 8 ⊢ Ⅎ𝑧 ¬ ∀𝑧 𝑧 = 𝑦
7	5, 6	nfan 2002	. . . . . . 7 ⊢ Ⅎ𝑧(¬ ∀𝑧 𝑧 = 𝑥 ∧ ¬ ∀𝑧 𝑧 = 𝑦)
8		nfcvf 2993	. . . . . . . . . 10 ⊢ (¬ ∀𝑧 𝑧 = 𝑥 → Ⅎ𝑧𝑥)
9	8	nfcrd 2976	. . . . . . . . 9 ⊢ (¬ ∀𝑧 𝑧 = 𝑥 → Ⅎ𝑧 𝑤 ∈ 𝑥)
10	9	adantr 474	. . . . . . . 8 ⊢ ((¬ ∀𝑧 𝑧 = 𝑥 ∧ ¬ ∀𝑧 𝑧 = 𝑦) → Ⅎ𝑧 𝑤 ∈ 𝑥)
11		nfcvf 2993	. . . . . . . . . . 11 ⊢ (¬ ∀𝑧 𝑧 = 𝑦 → Ⅎ𝑧𝑦)
12	11	nfcrd 2976	. . . . . . . . . 10 ⊢ (¬ ∀𝑧 𝑧 = 𝑦 → Ⅎ𝑧 𝑤 ∈ 𝑦)
13	12	nfnd 1958	. . . . . . . . 9 ⊢ (¬ ∀𝑧 𝑧 = 𝑦 → Ⅎ𝑧 ¬ 𝑤 ∈ 𝑦)
14	13	adantl 475	. . . . . . . 8 ⊢ ((¬ ∀𝑧 𝑧 = 𝑥 ∧ ¬ ∀𝑧 𝑧 = 𝑦) → Ⅎ𝑧 ¬ 𝑤 ∈ 𝑦)
15	10, 14	nfimd 1996	. . . . . . 7 ⊢ ((¬ ∀𝑧 𝑧 = 𝑥 ∧ ¬ ∀𝑧 𝑧 = 𝑦) → Ⅎ𝑧(𝑤 ∈ 𝑥 → ¬ 𝑤 ∈ 𝑦))
16		elequ1 2171	. . . . . . . . 9 ⊢ (𝑤 = 𝑧 → (𝑤 ∈ 𝑥 ↔ 𝑧 ∈ 𝑥))
17		elequ1 2171	. . . . . . . . . 10 ⊢ (𝑤 = 𝑧 → (𝑤 ∈ 𝑦 ↔ 𝑧 ∈ 𝑦))
18	17	notbid 310	. . . . . . . . 9 ⊢ (𝑤 = 𝑧 → (¬ 𝑤 ∈ 𝑦 ↔ ¬ 𝑧 ∈ 𝑦))
19	16, 18	imbi12d 336	. . . . . . . 8 ⊢ (𝑤 = 𝑧 → ((𝑤 ∈ 𝑥 → ¬ 𝑤 ∈ 𝑦) ↔ (𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦)))
20	19	a1i 11	. . . . . . 7 ⊢ ((¬ ∀𝑧 𝑧 = 𝑥 ∧ ¬ ∀𝑧 𝑧 = 𝑦) → (𝑤 = 𝑧 → ((𝑤 ∈ 𝑥 → ¬ 𝑤 ∈ 𝑦) ↔ (𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))))
21	7, 15, 20	cbvald 2427	. . . . . 6 ⊢ ((¬ ∀𝑧 𝑧 = 𝑥 ∧ ¬ ∀𝑧 𝑧 = 𝑦) → (∀𝑤(𝑤 ∈ 𝑥 → ¬ 𝑤 ∈ 𝑦) ↔ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦)))
22	21	anbi2d 622	. . . . 5 ⊢ ((¬ ∀𝑧 𝑧 = 𝑥 ∧ ¬ ∀𝑧 𝑧 = 𝑦) → ((𝑥 ∈ 𝑦 ∧ ∀𝑤(𝑤 ∈ 𝑥 → ¬ 𝑤 ∈ 𝑦)) ↔ (𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))))
23	4, 22	exbid 2266	. . . 4 ⊢ ((¬ ∀𝑧 𝑧 = 𝑥 ∧ ¬ ∀𝑧 𝑧 = 𝑦) → (∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑤(𝑤 ∈ 𝑥 → ¬ 𝑤 ∈ 𝑦)) ↔ ∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))))
24	1, 23	syl5ib 236	. . 3 ⊢ ((¬ ∀𝑧 𝑧 = 𝑥 ∧ ¬ ∀𝑧 𝑧 = 𝑦) → (𝑥 ∈ 𝑦 → ∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))))
25	24	ex 403	. 2 ⊢ (¬ ∀𝑧 𝑧 = 𝑥 → (¬ ∀𝑧 𝑧 = 𝑦 → (𝑥 ∈ 𝑦 → ∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦)))))
26		axregndlem1 9739	. . 3 ⊢ (∀𝑥 𝑥 = 𝑧 → (𝑥 ∈ 𝑦 → ∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))))
27	26	aecoms 2449	. 2 ⊢ (∀𝑧 𝑧 = 𝑥 → (𝑥 ∈ 𝑦 → ∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))))
28		19.8a 2223	. . 3 ⊢ (𝑥 ∈ 𝑦 → ∃𝑥 𝑥 ∈ 𝑦)
29		nfae 2453	. . . 4 ⊢ Ⅎ𝑥∀𝑧 𝑧 = 𝑦
30		elirrv 8770	. . . . . . . . 9 ⊢ ¬ 𝑧 ∈ 𝑧
31		elequ2 2178	. . . . . . . . 9 ⊢ (𝑧 = 𝑦 → (𝑧 ∈ 𝑧 ↔ 𝑧 ∈ 𝑦))
32	30, 31	mtbii 318	. . . . . . . 8 ⊢ (𝑧 = 𝑦 → ¬ 𝑧 ∈ 𝑦)
33	32	a1d 25	. . . . . . 7 ⊢ (𝑧 = 𝑦 → (𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))
34	33	alimi 1910	. . . . . 6 ⊢ (∀𝑧 𝑧 = 𝑦 → ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))
35	34	anim2i 610	. . . . 5 ⊢ ((𝑥 ∈ 𝑦 ∧ ∀𝑧 𝑧 = 𝑦) → (𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦)))
36	35	expcom 404	. . . 4 ⊢ (∀𝑧 𝑧 = 𝑦 → (𝑥 ∈ 𝑦 → (𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))))
37	29, 36	eximd 2259	. . 3 ⊢ (∀𝑧 𝑧 = 𝑦 → (∃𝑥 𝑥 ∈ 𝑦 → ∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))))
38	28, 37	syl5 34	. 2 ⊢ (∀𝑧 𝑧 = 𝑦 → (𝑥 ∈ 𝑦 → ∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦))))
39	25, 27, 38	pm2.61ii 178	1 ⊢ (𝑥 ∈ 𝑦 → ∃𝑥(𝑥 ∈ 𝑦 ∧ ∀𝑧(𝑧 ∈ 𝑥 → ¬ 𝑧 ∈ 𝑦)))

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 198   ∧ wa 386  ∀wal 1654  ∃wex 1878  Ⅎwnf 1882

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-8 2166  ax-9 2173  ax-10 2192  ax-11 2207  ax-12 2220  ax-13 2389  ax-ext 2803  ax-sep 5005  ax-nul 5013  ax-pr 5127  ax-reg 8766

This theorem depends on definitions:  df-bi 199  df-an 387  df-or 879  df-tru 1660  df-ex 1879  df-nf 1883  df-sb 2068  df-clab 2812  df-cleq 2818  df-clel 2821  df-nfc 2958  df-ral 3122  df-rex 3123  df-v 3416  df-dif 3801  df-un 3803  df-nul 4145  df-sn 4398  df-pr 4400

This theorem is referenced by:  zfcndreg  9754  axregprim  32115