| Step | Hyp | Ref
 | Expression | 
| 1 |   | suceq 4437 | 
. . . 4
⊢ (𝑤 = ∅ → suc 𝑤 = suc ∅) | 
| 2 |   | id 19 | 
. . . 4
⊢ (𝑤 = ∅ → 𝑤 = ∅) | 
| 3 | 1, 2 | breq12d 4046 | 
. . 3
⊢ (𝑤 = ∅ → (suc 𝑤 ≼ 𝑤 ↔ suc ∅ ≼
∅)) | 
| 4 | 3 | notbid 668 | 
. 2
⊢ (𝑤 = ∅ → (¬ suc
𝑤 ≼ 𝑤 ↔ ¬ suc ∅
≼ ∅)) | 
| 5 |   | suceq 4437 | 
. . . 4
⊢ (𝑤 = 𝑘 → suc 𝑤 = suc 𝑘) | 
| 6 |   | id 19 | 
. . . 4
⊢ (𝑤 = 𝑘 → 𝑤 = 𝑘) | 
| 7 | 5, 6 | breq12d 4046 | 
. . 3
⊢ (𝑤 = 𝑘 → (suc 𝑤 ≼ 𝑤 ↔ suc 𝑘 ≼ 𝑘)) | 
| 8 | 7 | notbid 668 | 
. 2
⊢ (𝑤 = 𝑘 → (¬ suc 𝑤 ≼ 𝑤 ↔ ¬ suc 𝑘 ≼ 𝑘)) | 
| 9 |   | suceq 4437 | 
. . . 4
⊢ (𝑤 = suc 𝑘 → suc 𝑤 = suc suc 𝑘) | 
| 10 |   | id 19 | 
. . . 4
⊢ (𝑤 = suc 𝑘 → 𝑤 = suc 𝑘) | 
| 11 | 9, 10 | breq12d 4046 | 
. . 3
⊢ (𝑤 = suc 𝑘 → (suc 𝑤 ≼ 𝑤 ↔ suc suc 𝑘 ≼ suc 𝑘)) | 
| 12 | 11 | notbid 668 | 
. 2
⊢ (𝑤 = suc 𝑘 → (¬ suc 𝑤 ≼ 𝑤 ↔ ¬ suc suc 𝑘 ≼ suc 𝑘)) | 
| 13 |   | suceq 4437 | 
. . . 4
⊢ (𝑤 = 𝐴 → suc 𝑤 = suc 𝐴) | 
| 14 |   | id 19 | 
. . . 4
⊢ (𝑤 = 𝐴 → 𝑤 = 𝐴) | 
| 15 | 13, 14 | breq12d 4046 | 
. . 3
⊢ (𝑤 = 𝐴 → (suc 𝑤 ≼ 𝑤 ↔ suc 𝐴 ≼ 𝐴)) | 
| 16 | 15 | notbid 668 | 
. 2
⊢ (𝑤 = 𝐴 → (¬ suc 𝑤 ≼ 𝑤 ↔ ¬ suc 𝐴 ≼ 𝐴)) | 
| 17 |   | peano1 4630 | 
. . . 4
⊢ ∅
∈ ω | 
| 18 |   | php5 6919 | 
. . . 4
⊢ (∅
∈ ω → ¬ ∅ ≈ suc ∅) | 
| 19 | 17, 18 | ax-mp 5 | 
. . 3
⊢  ¬
∅ ≈ suc ∅ | 
| 20 |   | 0ex 4160 | 
. . . . . 6
⊢ ∅
∈ V | 
| 21 | 20 | domen 6810 | 
. . . . 5
⊢ (suc
∅ ≼ ∅ ↔ ∃𝑥(suc ∅ ≈ 𝑥 ∧ 𝑥 ⊆ ∅)) | 
| 22 |   | ss0 3491 | 
. . . . . . . 8
⊢ (𝑥 ⊆ ∅ → 𝑥 = ∅) | 
| 23 |   | en0 6854 | 
. . . . . . . 8
⊢ (𝑥 ≈ ∅ ↔ 𝑥 = ∅) | 
| 24 | 22, 23 | sylibr 134 | 
. . . . . . 7
⊢ (𝑥 ⊆ ∅ → 𝑥 ≈
∅) | 
| 25 |   | entr 6843 | 
. . . . . . 7
⊢ ((suc
∅ ≈ 𝑥 ∧
𝑥 ≈ ∅) →
suc ∅ ≈ ∅) | 
| 26 | 24, 25 | sylan2 286 | 
. . . . . 6
⊢ ((suc
∅ ≈ 𝑥 ∧
𝑥 ⊆ ∅) →
suc ∅ ≈ ∅) | 
| 27 | 26 | exlimiv 1612 | 
. . . . 5
⊢
(∃𝑥(suc
∅ ≈ 𝑥 ∧
𝑥 ⊆ ∅) →
suc ∅ ≈ ∅) | 
| 28 | 21, 27 | sylbi 121 | 
. . . 4
⊢ (suc
∅ ≼ ∅ → suc ∅ ≈ ∅) | 
| 29 | 28 | ensymd 6842 | 
. . 3
⊢ (suc
∅ ≼ ∅ → ∅ ≈ suc ∅) | 
| 30 | 19, 29 | mto 663 | 
. 2
⊢  ¬
suc ∅ ≼ ∅ | 
| 31 |   | peano2 4631 | 
. . . 4
⊢ (𝑘 ∈ ω → suc 𝑘 ∈
ω) | 
| 32 |   | phplem4dom 6923 | 
. . . 4
⊢ ((suc
𝑘 ∈ ω ∧
𝑘 ∈ ω) →
(suc suc 𝑘 ≼ suc
𝑘 → suc 𝑘 ≼ 𝑘)) | 
| 33 | 31, 32 | mpancom 422 | 
. . 3
⊢ (𝑘 ∈ ω → (suc suc
𝑘 ≼ suc 𝑘 → suc 𝑘 ≼ 𝑘)) | 
| 34 | 33 | con3d 632 | 
. 2
⊢ (𝑘 ∈ ω → (¬
suc 𝑘 ≼ 𝑘 → ¬ suc suc 𝑘 ≼ suc 𝑘)) | 
| 35 | 4, 8, 12, 16, 30, 34 | finds 4636 | 
1
⊢ (𝐴 ∈ ω → ¬ suc
𝐴 ≼ 𝐴) |