Theorem wl-mo2df 32531

Description: Version of mo2 2467 with a context and a distinctor replacing a distinct variable condition. This version should be used only to eliminate dv conditions. (Contributed by Wolf Lammen, 11-Aug-2019.)

Hypotheses

Ref	Expression
wl-mo2df.1	⊢ Ⅎ𝑥𝜑
wl-mo2df.2	⊢ Ⅎ𝑦𝜑
wl-mo2df.3	⊢ (𝜑 → ¬ ∀𝑥 𝑥 = 𝑦)
wl-mo2df.4	⊢ (𝜑 → Ⅎ𝑦𝜓)

Assertion

Ref	Expression
wl-mo2df	⊢ (𝜑 → (∃*𝑥𝜓 ↔ ∃𝑦∀𝑥(𝜓 → 𝑥 = 𝑦)))

Proof of Theorem wl-mo2df

Dummy variable 𝑢 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		mo2v 2465	. 2 ⊢ (∃*𝑥𝜓 ↔ ∃𝑢∀𝑥(𝜓 → 𝑥 = 𝑢))
2		wl-mo2df.2	. . 3 ⊢ Ⅎ𝑦𝜑
3		wl-mo2df.1	. . . 4 ⊢ Ⅎ𝑥𝜑
4		wl-mo2df.4	. . . . 5 ⊢ (𝜑 → Ⅎ𝑦𝜓)
5		wl-mo2df.3	. . . . . 6 ⊢ (𝜑 → ¬ ∀𝑥 𝑥 = 𝑦)
6		nfeqf1 2287	. . . . . . 7 ⊢ (¬ ∀𝑦 𝑦 = 𝑥 → Ⅎ𝑦 𝑥 = 𝑢)
7	6	naecoms 2301	. . . . . 6 ⊢ (¬ ∀𝑥 𝑥 = 𝑦 → Ⅎ𝑦 𝑥 = 𝑢)
8	5, 7	syl 17	. . . . 5 ⊢ (𝜑 → Ⅎ𝑦 𝑥 = 𝑢)
9	4, 8	nfimd 1812	. . . 4 ⊢ (𝜑 → Ⅎ𝑦(𝜓 → 𝑥 = 𝑢))
10	3, 9	nfald 2151	. . 3 ⊢ (𝜑 → Ⅎ𝑦∀𝑥(𝜓 → 𝑥 = 𝑢))
11		nfnae 2306	. . . . . . 7 ⊢ Ⅎ𝑥 ¬ ∀𝑥 𝑥 = 𝑦
12		nfeqf2 2285	. . . . . . 7 ⊢ (¬ ∀𝑥 𝑥 = 𝑦 → Ⅎ𝑥 𝑢 = 𝑦)
13	11, 12	nfan1 2056	. . . . . 6 ⊢ Ⅎ𝑥(¬ ∀𝑥 𝑥 = 𝑦 ∧ 𝑢 = 𝑦)
14		equequ2 1940	. . . . . . . 8 ⊢ (𝑢 = 𝑦 → (𝑥 = 𝑢 ↔ 𝑥 = 𝑦))
15	14	imbi2d 329	. . . . . . 7 ⊢ (𝑢 = 𝑦 → ((𝜓 → 𝑥 = 𝑢) ↔ (𝜓 → 𝑥 = 𝑦)))
16	15	adantl 481	. . . . . 6 ⊢ ((¬ ∀𝑥 𝑥 = 𝑦 ∧ 𝑢 = 𝑦) → ((𝜓 → 𝑥 = 𝑢) ↔ (𝜓 → 𝑥 = 𝑦)))
17	13, 16	albid 2077	. . . . 5 ⊢ ((¬ ∀𝑥 𝑥 = 𝑦 ∧ 𝑢 = 𝑦) → (∀𝑥(𝜓 → 𝑥 = 𝑢) ↔ ∀𝑥(𝜓 → 𝑥 = 𝑦)))
18	5, 17	sylan 487	. . . 4 ⊢ ((𝜑 ∧ 𝑢 = 𝑦) → (∀𝑥(𝜓 → 𝑥 = 𝑢) ↔ ∀𝑥(𝜓 → 𝑥 = 𝑦)))
19	18	ex 449	. . 3 ⊢ (𝜑 → (𝑢 = 𝑦 → (∀𝑥(𝜓 → 𝑥 = 𝑢) ↔ ∀𝑥(𝜓 → 𝑥 = 𝑦))))
20	2, 10, 19	cbvexd 2266	. 2 ⊢ (𝜑 → (∃𝑢∀𝑥(𝜓 → 𝑥 = 𝑢) ↔ ∃𝑦∀𝑥(𝜓 → 𝑥 = 𝑦)))
21	1, 20	syl5bb 271	1 ⊢ (𝜑 → (∃*𝑥𝜓 ↔ ∃𝑦∀𝑥(𝜓 → 𝑥 = 𝑦)))

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 195   ∧ wa 383  ∀wal 1473  ∃wex 1695  Ⅎwnf 1699  ∃*wmo 2459

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1713  ax-4 1728  ax-5 1827  ax-6 1875  ax-7 1922  ax-10 2006  ax-11 2021  ax-12 2034  ax-13 2234

This theorem depends on definitions:  df-bi 196  df-or 384  df-an 385  df-tru 1478  df-ex 1696  df-nf 1701  df-eu 2462  df-mo 2463

This theorem is referenced by:  wl-mo2tf  32532