Theorem abnexg 7756

Description: Sufficient condition for a class abstraction to be a proper class. The class 𝐹 can be thought of as an expression in 𝑥 and the abstraction appearing in the statement as the class of values 𝐹 as 𝑥 varies through 𝐴. Assuming the antecedents, if that class is a set, then so is the "domain" 𝐴. The converse holds without antecedent, see abrexexg 7959. Note that the second antecedent ∀𝑥 ∈ 𝐴𝑥 ∈ 𝐹 cannot be translated to 𝐴 ⊆ 𝐹 since 𝐹 may depend on 𝑥. In applications, one may take 𝐹 = {𝑥} or 𝐹 = 𝒫 𝑥 (see snnex 7758 and pwnex 7759 respectively, proved from abnex 7757, which is a consequence of abnexg 7756 with 𝐴 = V). (Contributed by BJ, 2-Dec-2021.)

Assertion

Ref	Expression
abnexg	⊢ (∀𝑥 ∈ 𝐴 (𝐹 ∈ 𝑉 ∧ 𝑥 ∈ 𝐹) → ({𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = 𝐹} ∈ 𝑊 → 𝐴 ∈ V))

Distinct variable groups:   𝑥,𝐴,𝑦   𝑦,𝐹

Allowed substitution hints:   𝐹(𝑥)   𝑉(𝑥, 𝑦)   𝑊(𝑥, 𝑦)

Proof of Theorem abnexg

Step	Hyp	Ref	Expression
1		uniexg 7743	. 2 ⊢ ({𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = 𝐹} ∈ 𝑊 → ∪ {𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = 𝐹} ∈ V)
2		simpl 488	. . . . 5 ⊢ ((𝐹 ∈ 𝑉 ∧ 𝑥 ∈ 𝐹) → 𝐹 ∈ 𝑉)
3	2	ralimi 3099	. . . 4 ⊢ (∀𝑥 ∈ 𝐴 (𝐹 ∈ 𝑉 ∧ 𝑥 ∈ 𝐹) → ∀𝑥 ∈ 𝐴 𝐹 ∈ 𝑉)
4		dfiun2g 4988	. . . . . 6 ⊢ (∀𝑥 ∈ 𝐴 𝐹 ∈ 𝑉 → ∪ 𝑥 ∈ 𝐴 𝐹 = ∪ {𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = 𝐹})
5	4	eleq1d 2845	. . . . 5 ⊢ (∀𝑥 ∈ 𝐴 𝐹 ∈ 𝑉 → (∪ 𝑥 ∈ 𝐴 𝐹 ∈ V ↔ ∪ {𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = 𝐹} ∈ V))
6	5	biimprd 251	. . . 4 ⊢ (∀𝑥 ∈ 𝐴 𝐹 ∈ 𝑉 → (∪ {𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = 𝐹} ∈ V → ∪ 𝑥 ∈ 𝐴 𝐹 ∈ V))
7	3, 6	syl 18	. . 3 ⊢ (∀𝑥 ∈ 𝐴 (𝐹 ∈ 𝑉 ∧ 𝑥 ∈ 𝐹) → (∪ {𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = 𝐹} ∈ V → ∪ 𝑥 ∈ 𝐴 𝐹 ∈ V))
8		simpr 490	. . . . 5 ⊢ ((𝐹 ∈ 𝑉 ∧ 𝑥 ∈ 𝐹) → 𝑥 ∈ 𝐹)
9	8	ralimi 3099	. . . 4 ⊢ (∀𝑥 ∈ 𝐴 (𝐹 ∈ 𝑉 ∧ 𝑥 ∈ 𝐹) → ∀𝑥 ∈ 𝐴 𝑥 ∈ 𝐹)
10		iunid 5019	. . . . 5 ⊢ ∪ 𝑥 ∈ 𝐴 {𝑥} = 𝐴
11		snssi 4746	. . . . . . 7 ⊢ (𝑥 ∈ 𝐹 → {𝑥} ⊆ 𝐹)
12	11	ralimi 3099	. . . . . 6 ⊢ (∀𝑥 ∈ 𝐴 𝑥 ∈ 𝐹 → ∀𝑥 ∈ 𝐴 {𝑥} ⊆ 𝐹)
13		ss2iun 4970	. . . . . 6 ⊢ (∀𝑥 ∈ 𝐴 {𝑥} ⊆ 𝐹 → ∪ 𝑥 ∈ 𝐴 {𝑥} ⊆ ∪ 𝑥 ∈ 𝐴 𝐹)
14	12, 13	syl 18	. . . . 5 ⊢ (∀𝑥 ∈ 𝐴 𝑥 ∈ 𝐹 → ∪ 𝑥 ∈ 𝐴 {𝑥} ⊆ ∪ 𝑥 ∈ 𝐴 𝐹)
15	10, 14	eqsstrrid 3970	. . . 4 ⊢ (∀𝑥 ∈ 𝐴 𝑥 ∈ 𝐹 → 𝐴 ⊆ ∪ 𝑥 ∈ 𝐴 𝐹)
16		ssexg 5284	. . . . 5 ⊢ ((𝐴 ⊆ ∪ 𝑥 ∈ 𝐴 𝐹 ∧ ∪ 𝑥 ∈ 𝐴 𝐹 ∈ V) → 𝐴 ∈ V)
17	16	ex 418	. . . 4 ⊢ (𝐴 ⊆ ∪ 𝑥 ∈ 𝐴 𝐹 → (∪ 𝑥 ∈ 𝐴 𝐹 ∈ V → 𝐴 ∈ V))
18	9, 15, 17	3syl 19	. . 3 ⊢ (∀𝑥 ∈ 𝐴 (𝐹 ∈ 𝑉 ∧ 𝑥 ∈ 𝐹) → (∪ 𝑥 ∈ 𝐴 𝐹 ∈ V → 𝐴 ∈ V))
19	7, 18	syld 48	. 2 ⊢ (∀𝑥 ∈ 𝐴 (𝐹 ∈ 𝑉 ∧ 𝑥 ∈ 𝐹) → (∪ {𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = 𝐹} ∈ V → 𝐴 ∈ V))
20	1, 19	syl5 35	1 ⊢ (∀𝑥 ∈ 𝐴 (𝐹 ∈ 𝑉 ∧ 𝑥 ∈ 𝐹) → ({𝑦 ∣ ∃𝑥 ∈ 𝐴 𝑦 = 𝐹} ∈ 𝑊 → 𝐴 ∈ V))

This proof depends on syntax axioms:   → wi 4   ∧ wa 401   = wceq 1570   ∈ wcel 2145  {cab 2738  ∀wral 3076  ∃wrex 3086  Vcvv 3450   ⊆ wss 3899  {csn 4584  ∪ cuni 4867  ∪ ciun 4951

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-8 2147  ax-9 2155  ax-11 2194  ax-ext 2732  ax-sep 5251  ax-un 7737

This proof depends on definitions:  df-bi 210  df-an 402  df-3an 1105  df-tru 1573  df-ex 1813  df-sb 2100  df-clab 2739  df-cleq 2752  df-clel 2835  df-ral 3077  df-rex 3087  df-rab 3413  df-v 3452  df-in 3906  df-ss 3916  df-sn 4585  df-uni 4868  df-iun 4953

This theorem is used by:  abnex  7757