| Step | Hyp | Ref | Expression | 
						
							| 1 |  | idn1 | ⊢ (    𝐴  ∈  𝐵    ▶    𝐴  ∈  𝐵    ) | 
						
							| 2 |  | idn2 | ⊢ (    𝐴  ∈  𝐵    ,    [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )    ▶    [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )    ) | 
						
							| 3 |  | sbcimg | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) ) ) ) | 
						
							| 4 | 3 | biimpd | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )  →  ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) ) ) ) | 
						
							| 5 | 1 2 4 | e12 | ⊢ (    𝐴  ∈  𝐵    ,    [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )    ▶    ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) )    ) | 
						
							| 6 |  | sbcimg | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) | 
						
							| 7 | 1 6 | e1a | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )    ) | 
						
							| 8 |  | imbi2 | ⊢ ( ( [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) ) | 
						
							| 9 | 8 | biimpcd | ⊢ ( ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) )  →  ( ( [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) ) | 
						
							| 10 | 5 7 9 | e21 | ⊢ (    𝐴  ∈  𝐵    ,    [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )    ▶    ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )    ) | 
						
							| 11 | 10 | in2 | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )  →  ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) ) )    ) | 
						
							| 12 |  | idn2 | ⊢ (    𝐴  ∈  𝐵    ,    ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )    ▶    ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )    ) | 
						
							| 13 |  | biimpr | ⊢ ( ( [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 )  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) ) ) | 
						
							| 14 | 13 | imim2d | ⊢ ( ( [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) ) ) ) | 
						
							| 15 | 7 12 14 | e12 | ⊢ (    𝐴  ∈  𝐵    ,    ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )    ▶    ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) )    ) | 
						
							| 16 | 1 3 | e1a | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) ) )    ) | 
						
							| 17 |  | biimpr | ⊢ ( ( [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) ) )  →  ( ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) )  →  [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) ) ) ) | 
						
							| 18 | 17 | com12 | ⊢ ( ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) )  →  ( ( [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  →  [ 𝐴  /  𝑥 ] ( 𝜓  →  𝜒 ) ) )  →  [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) ) ) ) | 
						
							| 19 | 15 16 18 | e21 | ⊢ (    𝐴  ∈  𝐵    ,    ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )    ▶    [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )    ) | 
						
							| 20 | 19 | in2 | ⊢ (    𝐴  ∈  𝐵    ▶    ( ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) ) )    ) | 
						
							| 21 |  | impbi | ⊢ ( ( [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )  →  ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) ) )  →  ( ( ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) ) )  →  ( [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) ) ) | 
						
							| 22 | 11 20 21 | e11 | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) ) )    ) | 
						
							| 23 | 22 | in1 | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑥 ] ( 𝜑  →  ( 𝜓  →  𝜒 ) )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  →  ( [ 𝐴  /  𝑥 ] 𝜓  →  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) ) |