| Step | Hyp | Ref
 | Expression | 
| 1 |   | nfv 1542 | 
. . . 4
⊢
Ⅎ𝑧(𝑥 ∈ 𝐴 → 𝜑) | 
| 2 |   | nfcsb1v 3117 | 
. . . . . 6
⊢
Ⅎ𝑥⦋𝑧 / 𝑥⦌𝐴 | 
| 3 | 2 | nfcri 2333 | 
. . . . 5
⊢
Ⅎ𝑥 𝑧 ∈ ⦋𝑧 / 𝑥⦌𝐴 | 
| 4 |   | nfsbc1v 3008 | 
. . . . 5
⊢
Ⅎ𝑥[𝑧 / 𝑥]𝜑 | 
| 5 | 3, 4 | nfim 1586 | 
. . . 4
⊢
Ⅎ𝑥(𝑧 ∈ ⦋𝑧 / 𝑥⦌𝐴 → [𝑧 / 𝑥]𝜑) | 
| 6 |   | id 19 | 
. . . . . 6
⊢ (𝑥 = 𝑧 → 𝑥 = 𝑧) | 
| 7 |   | csbeq1a 3093 | 
. . . . . 6
⊢ (𝑥 = 𝑧 → 𝐴 = ⦋𝑧 / 𝑥⦌𝐴) | 
| 8 | 6, 7 | eleq12d 2267 | 
. . . . 5
⊢ (𝑥 = 𝑧 → (𝑥 ∈ 𝐴 ↔ 𝑧 ∈ ⦋𝑧 / 𝑥⦌𝐴)) | 
| 9 |   | sbceq1a 2999 | 
. . . . 5
⊢ (𝑥 = 𝑧 → (𝜑 ↔ [𝑧 / 𝑥]𝜑)) | 
| 10 | 8, 9 | imbi12d 234 | 
. . . 4
⊢ (𝑥 = 𝑧 → ((𝑥 ∈ 𝐴 → 𝜑) ↔ (𝑧 ∈ ⦋𝑧 / 𝑥⦌𝐴 → [𝑧 / 𝑥]𝜑))) | 
| 11 | 1, 5, 10 | cbval 1768 | 
. . 3
⊢
(∀𝑥(𝑥 ∈ 𝐴 → 𝜑) ↔ ∀𝑧(𝑧 ∈ ⦋𝑧 / 𝑥⦌𝐴 → [𝑧 / 𝑥]𝜑)) | 
| 12 |   | nfcv 2339 | 
. . . . . . 7
⊢
Ⅎ𝑦𝑧 | 
| 13 |   | cbvralcsf.1 | 
. . . . . . 7
⊢
Ⅎ𝑦𝐴 | 
| 14 | 12, 13 | nfcsb 3122 | 
. . . . . 6
⊢
Ⅎ𝑦⦋𝑧 / 𝑥⦌𝐴 | 
| 15 | 14 | nfcri 2333 | 
. . . . 5
⊢
Ⅎ𝑦 𝑧 ∈ ⦋𝑧 / 𝑥⦌𝐴 | 
| 16 |   | cbvralcsf.3 | 
. . . . . 6
⊢
Ⅎ𝑦𝜑 | 
| 17 | 12, 16 | nfsbc 3010 | 
. . . . 5
⊢
Ⅎ𝑦[𝑧 / 𝑥]𝜑 | 
| 18 | 15, 17 | nfim 1586 | 
. . . 4
⊢
Ⅎ𝑦(𝑧 ∈ ⦋𝑧 / 𝑥⦌𝐴 → [𝑧 / 𝑥]𝜑) | 
| 19 |   | nfv 1542 | 
. . . 4
⊢
Ⅎ𝑧(𝑦 ∈ 𝐵 → 𝜓) | 
| 20 |   | id 19 | 
. . . . . 6
⊢ (𝑧 = 𝑦 → 𝑧 = 𝑦) | 
| 21 |   | csbeq1 3087 | 
. . . . . . 7
⊢ (𝑧 = 𝑦 → ⦋𝑧 / 𝑥⦌𝐴 = ⦋𝑦 / 𝑥⦌𝐴) | 
| 22 |   | df-csb 3085 | 
. . . . . . . 8
⊢
⦋𝑦 /
𝑥⦌𝐴 = {𝑣 ∣ [𝑦 / 𝑥]𝑣 ∈ 𝐴} | 
| 23 |   | cbvralcsf.2 | 
. . . . . . . . . . . 12
⊢
Ⅎ𝑥𝐵 | 
| 24 | 23 | nfcri 2333 | 
. . . . . . . . . . 11
⊢
Ⅎ𝑥 𝑣 ∈ 𝐵 | 
| 25 |   | cbvralcsf.5 | 
. . . . . . . . . . . 12
⊢ (𝑥 = 𝑦 → 𝐴 = 𝐵) | 
| 26 | 25 | eleq2d 2266 | 
. . . . . . . . . . 11
⊢ (𝑥 = 𝑦 → (𝑣 ∈ 𝐴 ↔ 𝑣 ∈ 𝐵)) | 
| 27 | 24, 26 | sbie 1805 | 
. . . . . . . . . 10
⊢ ([𝑦 / 𝑥]𝑣 ∈ 𝐴 ↔ 𝑣 ∈ 𝐵) | 
| 28 |   | sbsbc 2993 | 
. . . . . . . . . 10
⊢ ([𝑦 / 𝑥]𝑣 ∈ 𝐴 ↔ [𝑦 / 𝑥]𝑣 ∈ 𝐴) | 
| 29 | 27, 28 | bitr3i 186 | 
. . . . . . . . 9
⊢ (𝑣 ∈ 𝐵 ↔ [𝑦 / 𝑥]𝑣 ∈ 𝐴) | 
| 30 | 29 | abbi2i 2311 | 
. . . . . . . 8
⊢ 𝐵 = {𝑣 ∣ [𝑦 / 𝑥]𝑣 ∈ 𝐴} | 
| 31 | 22, 30 | eqtr4i 2220 | 
. . . . . . 7
⊢
⦋𝑦 /
𝑥⦌𝐴 = 𝐵 | 
| 32 | 21, 31 | eqtrdi 2245 | 
. . . . . 6
⊢ (𝑧 = 𝑦 → ⦋𝑧 / 𝑥⦌𝐴 = 𝐵) | 
| 33 | 20, 32 | eleq12d 2267 | 
. . . . 5
⊢ (𝑧 = 𝑦 → (𝑧 ∈ ⦋𝑧 / 𝑥⦌𝐴 ↔ 𝑦 ∈ 𝐵)) | 
| 34 |   | dfsbcq 2991 | 
. . . . . 6
⊢ (𝑧 = 𝑦 → ([𝑧 / 𝑥]𝜑 ↔ [𝑦 / 𝑥]𝜑)) | 
| 35 |   | sbsbc 2993 | 
. . . . . . 7
⊢ ([𝑦 / 𝑥]𝜑 ↔ [𝑦 / 𝑥]𝜑) | 
| 36 |   | cbvralcsf.4 | 
. . . . . . . 8
⊢
Ⅎ𝑥𝜓 | 
| 37 |   | cbvralcsf.6 | 
. . . . . . . 8
⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) | 
| 38 | 36, 37 | sbie 1805 | 
. . . . . . 7
⊢ ([𝑦 / 𝑥]𝜑 ↔ 𝜓) | 
| 39 | 35, 38 | bitr3i 186 | 
. . . . . 6
⊢
([𝑦 / 𝑥]𝜑 ↔ 𝜓) | 
| 40 | 34, 39 | bitrdi 196 | 
. . . . 5
⊢ (𝑧 = 𝑦 → ([𝑧 / 𝑥]𝜑 ↔ 𝜓)) | 
| 41 | 33, 40 | imbi12d 234 | 
. . . 4
⊢ (𝑧 = 𝑦 → ((𝑧 ∈ ⦋𝑧 / 𝑥⦌𝐴 → [𝑧 / 𝑥]𝜑) ↔ (𝑦 ∈ 𝐵 → 𝜓))) | 
| 42 | 18, 19, 41 | cbval 1768 | 
. . 3
⊢
(∀𝑧(𝑧 ∈ ⦋𝑧 / 𝑥⦌𝐴 → [𝑧 / 𝑥]𝜑) ↔ ∀𝑦(𝑦 ∈ 𝐵 → 𝜓)) | 
| 43 | 11, 42 | bitri 184 | 
. 2
⊢
(∀𝑥(𝑥 ∈ 𝐴 → 𝜑) ↔ ∀𝑦(𝑦 ∈ 𝐵 → 𝜓)) | 
| 44 |   | df-ral 2480 | 
. 2
⊢
(∀𝑥 ∈
𝐴 𝜑 ↔ ∀𝑥(𝑥 ∈ 𝐴 → 𝜑)) | 
| 45 |   | df-ral 2480 | 
. 2
⊢
(∀𝑦 ∈
𝐵 𝜓 ↔ ∀𝑦(𝑦 ∈ 𝐵 → 𝜓)) | 
| 46 | 43, 44, 45 | 3bitr4i 212 | 
1
⊢
(∀𝑥 ∈
𝐴 𝜑 ↔ ∀𝑦 ∈ 𝐵 𝜓) |