| Step | Hyp | Ref | Expression | 
						
							| 1 |  | axrepnd | ⊢ ∃ 𝑥 ( ∃ 𝑦 ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  →  ∀ 𝑧 ( ∀ 𝑦 𝑧  ∈  𝑥  ↔  ∃ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  ∧  ∀ 𝑦 𝜑 ) ) ) | 
						
							| 2 |  | df-ex | ⊢ ( ∃ 𝑦 ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  ↔  ¬  ∀ 𝑦 ¬  ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 ) ) | 
						
							| 3 |  | df-an | ⊢ ( ( ∀ 𝑧 𝑥  ∈  𝑦  ∧  ∀ 𝑦 𝜑 )  ↔  ¬  ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) ) | 
						
							| 4 | 3 | exbii | ⊢ ( ∃ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  ∧  ∀ 𝑦 𝜑 )  ↔  ∃ 𝑥 ¬  ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) ) | 
						
							| 5 |  | exnal | ⊢ ( ∃ 𝑥 ¬  ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 )  ↔  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) ) | 
						
							| 6 | 4 5 | bitri | ⊢ ( ∃ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  ∧  ∀ 𝑦 𝜑 )  ↔  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) ) | 
						
							| 7 | 6 | bibi2i | ⊢ ( ( ∀ 𝑦 𝑧  ∈  𝑥  ↔  ∃ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  ∧  ∀ 𝑦 𝜑 ) )  ↔  ( ∀ 𝑦 𝑧  ∈  𝑥  ↔  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) ) ) | 
						
							| 8 |  | dfbi1 | ⊢ ( ( ∀ 𝑦 𝑧  ∈  𝑥  ↔  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) )  ↔  ¬  ( ( ∀ 𝑦 𝑧  ∈  𝑥  →  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) )  →  ¬  ( ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 )  →  ∀ 𝑦 𝑧  ∈  𝑥 ) ) ) | 
						
							| 9 | 7 8 | bitri | ⊢ ( ( ∀ 𝑦 𝑧  ∈  𝑥  ↔  ∃ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  ∧  ∀ 𝑦 𝜑 ) )  ↔  ¬  ( ( ∀ 𝑦 𝑧  ∈  𝑥  →  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) )  →  ¬  ( ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 )  →  ∀ 𝑦 𝑧  ∈  𝑥 ) ) ) | 
						
							| 10 | 9 | albii | ⊢ ( ∀ 𝑧 ( ∀ 𝑦 𝑧  ∈  𝑥  ↔  ∃ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  ∧  ∀ 𝑦 𝜑 ) )  ↔  ∀ 𝑧 ¬  ( ( ∀ 𝑦 𝑧  ∈  𝑥  →  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) )  →  ¬  ( ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 )  →  ∀ 𝑦 𝑧  ∈  𝑥 ) ) ) | 
						
							| 11 | 2 10 | imbi12i | ⊢ ( ( ∃ 𝑦 ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  →  ∀ 𝑧 ( ∀ 𝑦 𝑧  ∈  𝑥  ↔  ∃ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  ∧  ∀ 𝑦 𝜑 ) ) )  ↔  ( ¬  ∀ 𝑦 ¬  ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  →  ∀ 𝑧 ¬  ( ( ∀ 𝑦 𝑧  ∈  𝑥  →  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) )  →  ¬  ( ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 )  →  ∀ 𝑦 𝑧  ∈  𝑥 ) ) ) ) | 
						
							| 12 | 11 | exbii | ⊢ ( ∃ 𝑥 ( ∃ 𝑦 ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  →  ∀ 𝑧 ( ∀ 𝑦 𝑧  ∈  𝑥  ↔  ∃ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  ∧  ∀ 𝑦 𝜑 ) ) )  ↔  ∃ 𝑥 ( ¬  ∀ 𝑦 ¬  ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  →  ∀ 𝑧 ¬  ( ( ∀ 𝑦 𝑧  ∈  𝑥  →  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) )  →  ¬  ( ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 )  →  ∀ 𝑦 𝑧  ∈  𝑥 ) ) ) ) | 
						
							| 13 |  | df-ex | ⊢ ( ∃ 𝑥 ( ¬  ∀ 𝑦 ¬  ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  →  ∀ 𝑧 ¬  ( ( ∀ 𝑦 𝑧  ∈  𝑥  →  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) )  →  ¬  ( ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 )  →  ∀ 𝑦 𝑧  ∈  𝑥 ) ) )  ↔  ¬  ∀ 𝑥 ¬  ( ¬  ∀ 𝑦 ¬  ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  →  ∀ 𝑧 ¬  ( ( ∀ 𝑦 𝑧  ∈  𝑥  →  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) )  →  ¬  ( ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 )  →  ∀ 𝑦 𝑧  ∈  𝑥 ) ) ) ) | 
						
							| 14 | 12 13 | bitri | ⊢ ( ∃ 𝑥 ( ∃ 𝑦 ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  →  ∀ 𝑧 ( ∀ 𝑦 𝑧  ∈  𝑥  ↔  ∃ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  ∧  ∀ 𝑦 𝜑 ) ) )  ↔  ¬  ∀ 𝑥 ¬  ( ¬  ∀ 𝑦 ¬  ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  →  ∀ 𝑧 ¬  ( ( ∀ 𝑦 𝑧  ∈  𝑥  →  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) )  →  ¬  ( ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 )  →  ∀ 𝑦 𝑧  ∈  𝑥 ) ) ) ) | 
						
							| 15 | 1 14 | mpbi | ⊢ ¬  ∀ 𝑥 ¬  ( ¬  ∀ 𝑦 ¬  ∀ 𝑧 ( 𝜑  →  𝑧  =  𝑦 )  →  ∀ 𝑧 ¬  ( ( ∀ 𝑦 𝑧  ∈  𝑥  →  ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 ) )  →  ¬  ( ¬  ∀ 𝑥 ( ∀ 𝑧 𝑥  ∈  𝑦  →  ¬  ∀ 𝑦 𝜑 )  →  ∀ 𝑦 𝑧  ∈  𝑥 ) ) ) |