Theorem dfom3 9568

Description: The class of natural numbers ω can be defined as the intersection of all inductive sets (which is the smallest inductive set, since inductive sets are closed under intersection), which is valid provided we assume the Axiom of Infinity. Definition 6.3 of [Eisenberg] p. 82. Definition 1.20 of [Schloeder] p. 3. (Contributed by NM, 6-Aug-1994.)

Assertion

Ref	Expression
dfom3	⊢ ω = ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)}

Distinct variable group:   𝑥,𝑦

Proof of Theorem dfom3

Dummy variable 𝑧 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		0ex 5254	. . . . 5 ⊢ ∅ ∈ V
2	1	elintab 4916	. . . 4 ⊢ (∅ ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)} ↔ ∀𝑥((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → ∅ ∈ 𝑥))
3		simpl 482	. . . 4 ⊢ ((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → ∅ ∈ 𝑥)
4	2, 3	mpgbir 1801	. . 3 ⊢ ∅ ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)}
5		suceq 6393	. . . . . . . . . 10 ⊢ (𝑦 = 𝑧 → suc 𝑦 = suc 𝑧)
6	5	eleq1d 2822	. . . . . . . . 9 ⊢ (𝑦 = 𝑧 → (suc 𝑦 ∈ 𝑥 ↔ suc 𝑧 ∈ 𝑥))
7	6	rspccv 3575	. . . . . . . 8 ⊢ (∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥 → (𝑧 ∈ 𝑥 → suc 𝑧 ∈ 𝑥))
8	7	adantl 481	. . . . . . 7 ⊢ ((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → (𝑧 ∈ 𝑥 → suc 𝑧 ∈ 𝑥))
9	8	a2i 14	. . . . . 6 ⊢ (((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → 𝑧 ∈ 𝑥) → ((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → suc 𝑧 ∈ 𝑥))
10	9	alimi 1813	. . . . 5 ⊢ (∀𝑥((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → 𝑧 ∈ 𝑥) → ∀𝑥((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → suc 𝑧 ∈ 𝑥))
11		vex 3446	. . . . . 6 ⊢ 𝑧 ∈ V
12	11	elintab 4916	. . . . 5 ⊢ (𝑧 ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)} ↔ ∀𝑥((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → 𝑧 ∈ 𝑥))
13	11	sucex 7761	. . . . . 6 ⊢ suc 𝑧 ∈ V
14	13	elintab 4916	. . . . 5 ⊢ (suc 𝑧 ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)} ↔ ∀𝑥((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → suc 𝑧 ∈ 𝑥))
15	10, 12, 14	3imtr4i 292	. . . 4 ⊢ (𝑧 ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)} → suc 𝑧 ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)})
16	15	rgenw 3056	. . 3 ⊢ ∀𝑧 ∈ ω (𝑧 ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)} → suc 𝑧 ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)})
17		peano5 7845	. . 3 ⊢ ((∅ ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)} ∧ ∀𝑧 ∈ ω (𝑧 ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)} → suc 𝑧 ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)})) → ω ⊆ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)})
18	4, 16, 17	mp2an 693	. 2 ⊢ ω ⊆ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)}
19		peano1 7841	. . . 4 ⊢ ∅ ∈ ω
20		peano2 7842	. . . . 5 ⊢ (𝑦 ∈ ω → suc 𝑦 ∈ ω)
21	20	rgen 3054	. . . 4 ⊢ ∀𝑦 ∈ ω suc 𝑦 ∈ ω
22		omex 9564	. . . . . 6 ⊢ ω ∈ V
23		eleq2 2826	. . . . . . . 8 ⊢ (𝑥 = ω → (∅ ∈ 𝑥 ↔ ∅ ∈ ω))
24		eleq2 2826	. . . . . . . . 9 ⊢ (𝑥 = ω → (suc 𝑦 ∈ 𝑥 ↔ suc 𝑦 ∈ ω))
25	24	raleqbi1dv 3310	. . . . . . . 8 ⊢ (𝑥 = ω → (∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥 ↔ ∀𝑦 ∈ ω suc 𝑦 ∈ ω))
26	23, 25	anbi12d 633	. . . . . . 7 ⊢ (𝑥 = ω → ((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) ↔ (∅ ∈ ω ∧ ∀𝑦 ∈ ω suc 𝑦 ∈ ω)))
27		eleq2 2826	. . . . . . 7 ⊢ (𝑥 = ω → (𝑧 ∈ 𝑥 ↔ 𝑧 ∈ ω))
28	26, 27	imbi12d 344	. . . . . 6 ⊢ (𝑥 = ω → (((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → 𝑧 ∈ 𝑥) ↔ ((∅ ∈ ω ∧ ∀𝑦 ∈ ω suc 𝑦 ∈ ω) → 𝑧 ∈ ω)))
29	22, 28	spcv 3561	. . . . 5 ⊢ (∀𝑥((∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥) → 𝑧 ∈ 𝑥) → ((∅ ∈ ω ∧ ∀𝑦 ∈ ω suc 𝑦 ∈ ω) → 𝑧 ∈ ω))
30	12, 29	sylbi 217	. . . 4 ⊢ (𝑧 ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)} → ((∅ ∈ ω ∧ ∀𝑦 ∈ ω suc 𝑦 ∈ ω) → 𝑧 ∈ ω))
31	19, 21, 30	mp2ani 699	. . 3 ⊢ (𝑧 ∈ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)} → 𝑧 ∈ ω)
32	31	ssriv 3939	. 2 ⊢ ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)} ⊆ ω
33	18, 32	eqssi 3952	1 ⊢ ω = ∩ {𝑥 ∣ (∅ ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 suc 𝑦 ∈ 𝑥)}

Syntax hints:   → wi 4   ∧ wa 395  ∀wal 1540   = wceq 1542   ∈ wcel 2114  {cab 2715  ∀wral 3052   ⊆ wss 3903  ∅c0 4287  ∩ cint 4904  suc csuc 6327  ωcom 7818

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1912  ax-6 1969  ax-7 2010  ax-8 2116  ax-9 2124  ax-10 2147  ax-11 2163  ax-12 2185  ax-ext 2709  ax-sep 5243  ax-nul 5253  ax-pr 5379  ax-un 7690  ax-inf2 9562

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 849  df-3or 1088  df-3an 1089  df-tru 1545  df-fal 1555  df-ex 1782  df-nf 1786  df-sb 2069  df-clab 2716  df-cleq 2729  df-clel 2812  df-ne 2934  df-ral 3053  df-rex 3063  df-rab 3402  df-v 3444  df-dif 3906  df-un 3908  df-in 3910  df-ss 3920  df-pss 3923  df-nul 4288  df-if 4482  df-pw 4558  df-sn 4583  df-pr 4585  df-op 4589  df-uni 4866  df-int 4905  df-br 5101  df-opab 5163  df-tr 5208  df-eprel 5532  df-po 5540  df-so 5541  df-fr 5585  df-we 5587  df-ord 6328  df-on 6329  df-lim 6330  df-suc 6331  df-om 7819

This theorem is referenced by: (None)