Theorem moabex 5401

Description: "At most one" existence implies a class abstraction exists. (Contributed by NM, 30-Dec-1996.) Avoid axioms. (Revised by SN, 2-Feb-2026.)

Assertion

Ref	Expression
moabex	⊢ (∃*𝑥𝜑 → {𝑥 ∣ 𝜑} ∈ V)

Proof of Theorem moabex

Dummy variable 𝑦 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		df-mo 2537	. 2 ⊢ (∃*𝑥𝜑 ↔ ∃𝑦∀𝑥(𝜑 → 𝑥 = 𝑦))
2		df-sn 4576	. . . . . 6 ⊢ {𝑦} = {𝑥 ∣ 𝑥 = 𝑦}
3		vsnex 5374	. . . . . 6 ⊢ {𝑦} ∈ V
4	2, 3	eqeltrri 2830	. . . . 5 ⊢ {𝑥 ∣ 𝑥 = 𝑦} ∈ V
5	4	a1i 11	. . . 4 ⊢ (∀𝑥(𝜑 → 𝑥 = 𝑦) → {𝑥 ∣ 𝑥 = 𝑦} ∈ V)
6		ss2abim 4009	. . . 4 ⊢ (∀𝑥(𝜑 → 𝑥 = 𝑦) → {𝑥 ∣ 𝜑} ⊆ {𝑥 ∣ 𝑥 = 𝑦})
7	5, 6	ssexd 5264	. . 3 ⊢ (∀𝑥(𝜑 → 𝑥 = 𝑦) → {𝑥 ∣ 𝜑} ∈ V)
8	7	exlimiv 1931	. 2 ⊢ (∃𝑦∀𝑥(𝜑 → 𝑥 = 𝑦) → {𝑥 ∣ 𝜑} ∈ V)
9	1, 8	sylbi 217	1 ⊢ (∃*𝑥𝜑 → {𝑥 ∣ 𝜑} ∈ V)

Syntax hints:   → wi 4  ∀wal 1539  ∃wex 1780   ∈ wcel 2113  ∃*wmo 2535  {cab 2711  Vcvv 3437  {csn 4575

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1796  ax-4 1810  ax-5 1911  ax-6 1968  ax-7 2009  ax-8 2115  ax-9 2123  ax-ext 2705  ax-sep 5236  ax-pr 5372

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-3an 1088  df-tru 1544  df-ex 1781  df-sb 2068  df-mo 2537  df-clab 2712  df-cleq 2725  df-clel 2808  df-rab 3397  df-v 3439  df-un 3903  df-in 3905  df-ss 3915  df-sn 4576  df-pr 4578

This theorem is referenced by:  rmorabex  5403  euabex  5404  satfv0  35423