Proof of Theorem dvelimfv
| Step | Hyp | Ref
 | Expression | 
| 1 |   | nfnae 1736 | 
. . . 4
⊢
Ⅎ𝑧 ¬
∀𝑥 𝑥 = 𝑦 | 
| 2 |   | ax12or 1522 | 
. . . . . . . . 9
⊢
(∀𝑥 𝑥 = 𝑧 ∨ (∀𝑥 𝑥 = 𝑦 ∨ ∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦))) | 
| 3 |   | orcom 729 | 
. . . . . . . . . 10
⊢
((∀𝑥 𝑥 = 𝑦 ∨ ∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦)) ↔ (∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦) ∨ ∀𝑥 𝑥 = 𝑦)) | 
| 4 | 3 | orbi2i 763 | 
. . . . . . . . 9
⊢
((∀𝑥 𝑥 = 𝑧 ∨ (∀𝑥 𝑥 = 𝑦 ∨ ∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦))) ↔ (∀𝑥 𝑥 = 𝑧 ∨ (∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦) ∨ ∀𝑥 𝑥 = 𝑦))) | 
| 5 | 2, 4 | mpbi 145 | 
. . . . . . . 8
⊢
(∀𝑥 𝑥 = 𝑧 ∨ (∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦) ∨ ∀𝑥 𝑥 = 𝑦)) | 
| 6 |   | orass 768 | 
. . . . . . . 8
⊢
(((∀𝑥 𝑥 = 𝑧 ∨ ∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦)) ∨ ∀𝑥 𝑥 = 𝑦) ↔ (∀𝑥 𝑥 = 𝑧 ∨ (∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦) ∨ ∀𝑥 𝑥 = 𝑦))) | 
| 7 | 5, 6 | mpbir 146 | 
. . . . . . 7
⊢
((∀𝑥 𝑥 = 𝑧 ∨ ∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦)) ∨ ∀𝑥 𝑥 = 𝑦) | 
| 8 |   | nfae 1733 | 
. . . . . . . . . . 11
⊢
Ⅎ𝑥∀𝑥 𝑥 = 𝑧 | 
| 9 |   | ax16ALT 1873 | 
. . . . . . . . . . 11
⊢
(∀𝑥 𝑥 = 𝑧 → (𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦)) | 
| 10 | 8, 9 | nfd 1537 | 
. . . . . . . . . 10
⊢
(∀𝑥 𝑥 = 𝑧 → Ⅎ𝑥 𝑧 = 𝑦) | 
| 11 |   | dvelimfv.1 | 
. . . . . . . . . . . 12
⊢ (𝜑 → ∀𝑥𝜑) | 
| 12 | 11 | nfi 1476 | 
. . . . . . . . . . 11
⊢
Ⅎ𝑥𝜑 | 
| 13 | 12 | a1i 9 | 
. . . . . . . . . 10
⊢
(∀𝑥 𝑥 = 𝑧 → Ⅎ𝑥𝜑) | 
| 14 | 10, 13 | nfimd 1599 | 
. . . . . . . . 9
⊢
(∀𝑥 𝑥 = 𝑧 → Ⅎ𝑥(𝑧 = 𝑦 → 𝜑)) | 
| 15 |   | df-nf 1475 | 
. . . . . . . . . 10
⊢
(Ⅎ𝑥 𝑧 = 𝑦 ↔ ∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦)) | 
| 16 |   | id 19 | 
. . . . . . . . . . 11
⊢
(Ⅎ𝑥 𝑧 = 𝑦 → Ⅎ𝑥 𝑧 = 𝑦) | 
| 17 | 12 | a1i 9 | 
. . . . . . . . . . 11
⊢
(Ⅎ𝑥 𝑧 = 𝑦 → Ⅎ𝑥𝜑) | 
| 18 | 16, 17 | nfimd 1599 | 
. . . . . . . . . 10
⊢
(Ⅎ𝑥 𝑧 = 𝑦 → Ⅎ𝑥(𝑧 = 𝑦 → 𝜑)) | 
| 19 | 15, 18 | sylbir 135 | 
. . . . . . . . 9
⊢
(∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦) → Ⅎ𝑥(𝑧 = 𝑦 → 𝜑)) | 
| 20 | 14, 19 | jaoi 717 | 
. . . . . . . 8
⊢
((∀𝑥 𝑥 = 𝑧 ∨ ∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦)) → Ⅎ𝑥(𝑧 = 𝑦 → 𝜑)) | 
| 21 | 20 | orim1i 761 | 
. . . . . . 7
⊢
(((∀𝑥 𝑥 = 𝑧 ∨ ∀𝑥(𝑧 = 𝑦 → ∀𝑥 𝑧 = 𝑦)) ∨ ∀𝑥 𝑥 = 𝑦) → (Ⅎ𝑥(𝑧 = 𝑦 → 𝜑) ∨ ∀𝑥 𝑥 = 𝑦)) | 
| 22 | 7, 21 | ax-mp 5 | 
. . . . . 6
⊢
(Ⅎ𝑥(𝑧 = 𝑦 → 𝜑) ∨ ∀𝑥 𝑥 = 𝑦) | 
| 23 |   | orcom 729 | 
. . . . . 6
⊢
((Ⅎ𝑥(𝑧 = 𝑦 → 𝜑) ∨ ∀𝑥 𝑥 = 𝑦) ↔ (∀𝑥 𝑥 = 𝑦 ∨ Ⅎ𝑥(𝑧 = 𝑦 → 𝜑))) | 
| 24 | 22, 23 | mpbi 145 | 
. . . . 5
⊢
(∀𝑥 𝑥 = 𝑦 ∨ Ⅎ𝑥(𝑧 = 𝑦 → 𝜑)) | 
| 25 | 24 | ori 724 | 
. . . 4
⊢ (¬
∀𝑥 𝑥 = 𝑦 → Ⅎ𝑥(𝑧 = 𝑦 → 𝜑)) | 
| 26 | 1, 25 | nfald 1774 | 
. . 3
⊢ (¬
∀𝑥 𝑥 = 𝑦 → Ⅎ𝑥∀𝑧(𝑧 = 𝑦 → 𝜑)) | 
| 27 |   | dvelimfv.2 | 
. . . . 5
⊢ (𝜓 → ∀𝑧𝜓) | 
| 28 |   | dvelimfv.3 | 
. . . . 5
⊢ (𝑧 = 𝑦 → (𝜑 ↔ 𝜓)) | 
| 29 | 27, 28 | equsalh 1740 | 
. . . 4
⊢
(∀𝑧(𝑧 = 𝑦 → 𝜑) ↔ 𝜓) | 
| 30 | 29 | nfbii 1487 | 
. . 3
⊢
(Ⅎ𝑥∀𝑧(𝑧 = 𝑦 → 𝜑) ↔ Ⅎ𝑥𝜓) | 
| 31 | 26, 30 | sylib 122 | 
. 2
⊢ (¬
∀𝑥 𝑥 = 𝑦 → Ⅎ𝑥𝜓) | 
| 32 | 31 | nfrd 1534 | 
1
⊢ (¬
∀𝑥 𝑥 = 𝑦 → (𝜓 → ∀𝑥𝜓)) |