| Step | Hyp | Ref | Expression | 
						
							| 1 |  | dftr2 | ⊢ ( Tr  𝒫  𝐴  ↔  ∀ 𝑧 ∀ 𝑦 ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )  →  𝑧  ∈  𝒫  𝐴 ) ) | 
						
							| 2 |  | idn1 | ⊢ (    Tr  𝐴    ▶    Tr  𝐴    ) | 
						
							| 3 |  | idn2 | ⊢ (    Tr  𝐴    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )    ▶    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )    ) | 
						
							| 4 |  | simpr | ⊢ ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )  →  𝑦  ∈  𝒫  𝐴 ) | 
						
							| 5 | 3 4 | e2 | ⊢ (    Tr  𝐴    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )    ▶    𝑦  ∈  𝒫  𝐴    ) | 
						
							| 6 |  | elpwi | ⊢ ( 𝑦  ∈  𝒫  𝐴  →  𝑦  ⊆  𝐴 ) | 
						
							| 7 | 5 6 | e2 | ⊢ (    Tr  𝐴    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )    ▶    𝑦  ⊆  𝐴    ) | 
						
							| 8 |  | simpl | ⊢ ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )  →  𝑧  ∈  𝑦 ) | 
						
							| 9 | 3 8 | e2 | ⊢ (    Tr  𝐴    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )    ▶    𝑧  ∈  𝑦    ) | 
						
							| 10 |  | ssel | ⊢ ( 𝑦  ⊆  𝐴  →  ( 𝑧  ∈  𝑦  →  𝑧  ∈  𝐴 ) ) | 
						
							| 11 | 7 9 10 | e22 | ⊢ (    Tr  𝐴    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )    ▶    𝑧  ∈  𝐴    ) | 
						
							| 12 |  | trss | ⊢ ( Tr  𝐴  →  ( 𝑧  ∈  𝐴  →  𝑧  ⊆  𝐴 ) ) | 
						
							| 13 | 2 11 12 | e12 | ⊢ (    Tr  𝐴    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )    ▶    𝑧  ⊆  𝐴    ) | 
						
							| 14 |  | vex | ⊢ 𝑧  ∈  V | 
						
							| 15 | 14 | elpw | ⊢ ( 𝑧  ∈  𝒫  𝐴  ↔  𝑧  ⊆  𝐴 ) | 
						
							| 16 | 13 15 | e2bir | ⊢ (    Tr  𝐴    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )    ▶    𝑧  ∈  𝒫  𝐴    ) | 
						
							| 17 | 16 | in2 | ⊢ (    Tr  𝐴    ▶    ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )  →  𝑧  ∈  𝒫  𝐴 )    ) | 
						
							| 18 | 17 | gen12 | ⊢ (    Tr  𝐴    ▶    ∀ 𝑧 ∀ 𝑦 ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )  →  𝑧  ∈  𝒫  𝐴 )    ) | 
						
							| 19 |  | biimpr | ⊢ ( ( Tr  𝒫  𝐴  ↔  ∀ 𝑧 ∀ 𝑦 ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )  →  𝑧  ∈  𝒫  𝐴 ) )  →  ( ∀ 𝑧 ∀ 𝑦 ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝒫  𝐴 )  →  𝑧  ∈  𝒫  𝐴 )  →  Tr  𝒫  𝐴 ) ) | 
						
							| 20 | 1 18 19 | e01 | ⊢ (    Tr  𝐴    ▶    Tr  𝒫  𝐴    ) | 
						
							| 21 | 20 | in1 | ⊢ ( Tr  𝐴  →  Tr  𝒫  𝐴 ) |