Theorem nfmod2 2556

Description: Bound-variable hypothesis builder for the at-most-one quantifier. Usage of this theorem is discouraged because it depends on ax-13 2375. See nfmodv 2557 for a version replacing the distinctor with a disjoint variable condition, not requiring ax-13 2375. (Contributed by Mario Carneiro, 14-Nov-2016.) Avoid df-eu 2567. (Revised by BJ, 14-Oct-2022.) (New usage is discouraged.)

Hypotheses

Ref	Expression
nfmod2.1	⊢ Ⅎ𝑦𝜑
nfmod2.2	⊢ ((𝜑 ∧ ¬ ∀𝑥 𝑥 = 𝑦) → Ⅎ𝑥𝜓)

Assertion

Ref	Expression
nfmod2	⊢ (𝜑 → Ⅎ𝑥∃*𝑦𝜓)

Proof of Theorem nfmod2

Dummy variable 𝑧 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		df-mo 2538	. 2 ⊢ (∃*𝑦𝜓 ↔ ∃𝑧∀𝑦(𝜓 → 𝑦 = 𝑧))
2		nfv 1912	. . 3 ⊢ Ⅎ𝑧𝜑
3		nfmod2.1	. . . 4 ⊢ Ⅎ𝑦𝜑
4		nfmod2.2	. . . . 5 ⊢ ((𝜑 ∧ ¬ ∀𝑥 𝑥 = 𝑦) → Ⅎ𝑥𝜓)
5		nfeqf1 2382	. . . . . 6 ⊢ (¬ ∀𝑥 𝑥 = 𝑦 → Ⅎ𝑥 𝑦 = 𝑧)
6	5	adantl 481	. . . . 5 ⊢ ((𝜑 ∧ ¬ ∀𝑥 𝑥 = 𝑦) → Ⅎ𝑥 𝑦 = 𝑧)
7	4, 6	nfimd 1892	. . . 4 ⊢ ((𝜑 ∧ ¬ ∀𝑥 𝑥 = 𝑦) → Ⅎ𝑥(𝜓 → 𝑦 = 𝑧))
8	3, 7	nfald2 2448	. . 3 ⊢ (𝜑 → Ⅎ𝑥∀𝑦(𝜓 → 𝑦 = 𝑧))
9	2, 8	nfexd 2328	. 2 ⊢ (𝜑 → Ⅎ𝑥∃𝑧∀𝑦(𝜓 → 𝑦 = 𝑧))
10	1, 9	nfxfrd 1851	1 ⊢ (𝜑 → Ⅎ𝑥∃*𝑦𝜓)

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 395  ∀wal 1535  ∃wex 1776  Ⅎwnf 1780  ∃*wmo 2536

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1792  ax-4 1806  ax-5 1908  ax-6 1965  ax-7 2005  ax-10 2139  ax-11 2155  ax-12 2175  ax-13 2375

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-tru 1540  df-ex 1777  df-nf 1781  df-mo 2538

This theorem is referenced by:  nfmod  2559  nfeud2  2588  nfrmod  3429  nfrmo  3431  nfdisj  5128