| Step | Hyp | Ref | Expression | 
						
							| 1 |  | ax-groth | ⊢ ∃ 𝑦 ( 𝑥  ∈  𝑦  ∧  ∀ 𝑧  ∈  𝑦 ( ∀ 𝑤 ( 𝑤  ⊆  𝑧  →  𝑤  ∈  𝑦 )  ∧  ∃ 𝑤  ∈  𝑦 ∀ 𝑣 ( 𝑣  ⊆  𝑧  →  𝑣  ∈  𝑤 ) )  ∧  ∀ 𝑧 ( 𝑧  ⊆  𝑦  →  ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) ) ) | 
						
							| 2 |  | biid | ⊢ ( 𝑥  ∈  𝑦  ↔  𝑥  ∈  𝑦 ) | 
						
							| 3 |  | pwss | ⊢ ( 𝒫  𝑧  ⊆  𝑦  ↔  ∀ 𝑤 ( 𝑤  ⊆  𝑧  →  𝑤  ∈  𝑦 ) ) | 
						
							| 4 |  | pwss | ⊢ ( 𝒫  𝑧  ⊆  𝑤  ↔  ∀ 𝑣 ( 𝑣  ⊆  𝑧  →  𝑣  ∈  𝑤 ) ) | 
						
							| 5 | 4 | rexbii | ⊢ ( ∃ 𝑤  ∈  𝑦 𝒫  𝑧  ⊆  𝑤  ↔  ∃ 𝑤  ∈  𝑦 ∀ 𝑣 ( 𝑣  ⊆  𝑧  →  𝑣  ∈  𝑤 ) ) | 
						
							| 6 | 3 5 | anbi12i | ⊢ ( ( 𝒫  𝑧  ⊆  𝑦  ∧  ∃ 𝑤  ∈  𝑦 𝒫  𝑧  ⊆  𝑤 )  ↔  ( ∀ 𝑤 ( 𝑤  ⊆  𝑧  →  𝑤  ∈  𝑦 )  ∧  ∃ 𝑤  ∈  𝑦 ∀ 𝑣 ( 𝑣  ⊆  𝑧  →  𝑣  ∈  𝑤 ) ) ) | 
						
							| 7 | 6 | ralbii | ⊢ ( ∀ 𝑧  ∈  𝑦 ( 𝒫  𝑧  ⊆  𝑦  ∧  ∃ 𝑤  ∈  𝑦 𝒫  𝑧  ⊆  𝑤 )  ↔  ∀ 𝑧  ∈  𝑦 ( ∀ 𝑤 ( 𝑤  ⊆  𝑧  →  𝑤  ∈  𝑦 )  ∧  ∃ 𝑤  ∈  𝑦 ∀ 𝑣 ( 𝑣  ⊆  𝑧  →  𝑣  ∈  𝑤 ) ) ) | 
						
							| 8 |  | df-ral | ⊢ ( ∀ 𝑧  ∈  𝒫  𝑦 ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 )  ↔  ∀ 𝑧 ( 𝑧  ∈  𝒫  𝑦  →  ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) ) ) | 
						
							| 9 |  | velpw | ⊢ ( 𝑧  ∈  𝒫  𝑦  ↔  𝑧  ⊆  𝑦 ) | 
						
							| 10 | 9 | imbi1i | ⊢ ( ( 𝑧  ∈  𝒫  𝑦  →  ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) )  ↔  ( 𝑧  ⊆  𝑦  →  ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) ) ) | 
						
							| 11 | 10 | albii | ⊢ ( ∀ 𝑧 ( 𝑧  ∈  𝒫  𝑦  →  ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) )  ↔  ∀ 𝑧 ( 𝑧  ⊆  𝑦  →  ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) ) ) | 
						
							| 12 | 8 11 | bitri | ⊢ ( ∀ 𝑧  ∈  𝒫  𝑦 ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 )  ↔  ∀ 𝑧 ( 𝑧  ⊆  𝑦  →  ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) ) ) | 
						
							| 13 | 2 7 12 | 3anbi123i | ⊢ ( ( 𝑥  ∈  𝑦  ∧  ∀ 𝑧  ∈  𝑦 ( 𝒫  𝑧  ⊆  𝑦  ∧  ∃ 𝑤  ∈  𝑦 𝒫  𝑧  ⊆  𝑤 )  ∧  ∀ 𝑧  ∈  𝒫  𝑦 ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) )  ↔  ( 𝑥  ∈  𝑦  ∧  ∀ 𝑧  ∈  𝑦 ( ∀ 𝑤 ( 𝑤  ⊆  𝑧  →  𝑤  ∈  𝑦 )  ∧  ∃ 𝑤  ∈  𝑦 ∀ 𝑣 ( 𝑣  ⊆  𝑧  →  𝑣  ∈  𝑤 ) )  ∧  ∀ 𝑧 ( 𝑧  ⊆  𝑦  →  ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) ) ) ) | 
						
							| 14 | 13 | exbii | ⊢ ( ∃ 𝑦 ( 𝑥  ∈  𝑦  ∧  ∀ 𝑧  ∈  𝑦 ( 𝒫  𝑧  ⊆  𝑦  ∧  ∃ 𝑤  ∈  𝑦 𝒫  𝑧  ⊆  𝑤 )  ∧  ∀ 𝑧  ∈  𝒫  𝑦 ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) )  ↔  ∃ 𝑦 ( 𝑥  ∈  𝑦  ∧  ∀ 𝑧  ∈  𝑦 ( ∀ 𝑤 ( 𝑤  ⊆  𝑧  →  𝑤  ∈  𝑦 )  ∧  ∃ 𝑤  ∈  𝑦 ∀ 𝑣 ( 𝑣  ⊆  𝑧  →  𝑣  ∈  𝑤 ) )  ∧  ∀ 𝑧 ( 𝑧  ⊆  𝑦  →  ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) ) ) ) | 
						
							| 15 | 1 14 | mpbir | ⊢ ∃ 𝑦 ( 𝑥  ∈  𝑦  ∧  ∀ 𝑧  ∈  𝑦 ( 𝒫  𝑧  ⊆  𝑦  ∧  ∃ 𝑤  ∈  𝑦 𝒫  𝑧  ⊆  𝑤 )  ∧  ∀ 𝑧  ∈  𝒫  𝑦 ( 𝑧  ≈  𝑦  ∨  𝑧  ∈  𝑦 ) ) |