| Step | Hyp | Ref | Expression | 
						
							| 1 |  | dfac10 | ⊢ ( CHOICE  ↔  dom  card  =  V ) | 
						
							| 2 |  | vex | ⊢ 𝑐  ∈  V | 
						
							| 3 |  | eleq2 | ⊢ ( dom  card  =  V  →  ( 𝑐  ∈  dom  card  ↔  𝑐  ∈  V ) ) | 
						
							| 4 | 2 3 | mpbiri | ⊢ ( dom  card  =  V  →  𝑐  ∈  dom  card ) | 
						
							| 5 |  | infxpidm2 | ⊢ ( ( 𝑐  ∈  dom  card  ∧  ω  ≼  𝑐 )  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 ) | 
						
							| 6 | 5 | ex | ⊢ ( 𝑐  ∈  dom  card  →  ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 ) ) | 
						
							| 7 | 4 6 | syl | ⊢ ( dom  card  =  V  →  ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 ) ) | 
						
							| 8 | 7 | alrimiv | ⊢ ( dom  card  =  V  →  ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 ) ) | 
						
							| 9 |  | finnum | ⊢ ( 𝑎  ∈  Fin  →  𝑎  ∈  dom  card ) | 
						
							| 10 | 9 | adantl | ⊢ ( ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  ∧  𝑎  ∈  Fin )  →  𝑎  ∈  dom  card ) | 
						
							| 11 |  | harcl | ⊢ ( har ‘ 𝑎 )  ∈  On | 
						
							| 12 |  | onenon | ⊢ ( ( har ‘ 𝑎 )  ∈  On  →  ( har ‘ 𝑎 )  ∈  dom  card ) | 
						
							| 13 | 11 12 | ax-mp | ⊢ ( har ‘ 𝑎 )  ∈  dom  card | 
						
							| 14 |  | fvex | ⊢ ( har ‘ 𝑎 )  ∈  V | 
						
							| 15 |  | vex | ⊢ 𝑎  ∈  V | 
						
							| 16 | 14 15 | unex | ⊢ ( ( har ‘ 𝑎 )  ∪  𝑎 )  ∈  V | 
						
							| 17 |  | harinf | ⊢ ( ( 𝑎  ∈  V  ∧  ¬  𝑎  ∈  Fin )  →  ω  ⊆  ( har ‘ 𝑎 ) ) | 
						
							| 18 | 15 17 | mpan | ⊢ ( ¬  𝑎  ∈  Fin  →  ω  ⊆  ( har ‘ 𝑎 ) ) | 
						
							| 19 |  | ssun1 | ⊢ ( har ‘ 𝑎 )  ⊆  ( ( har ‘ 𝑎 )  ∪  𝑎 ) | 
						
							| 20 | 18 19 | sstrdi | ⊢ ( ¬  𝑎  ∈  Fin  →  ω  ⊆  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) | 
						
							| 21 |  | ssdomg | ⊢ ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ∈  V  →  ( ω  ⊆  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  ω  ≼  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) ) | 
						
							| 22 | 16 20 21 | mpsyl | ⊢ ( ¬  𝑎  ∈  Fin  →  ω  ≼  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) | 
						
							| 23 |  | breq2 | ⊢ ( 𝑐  =  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  ( ω  ≼  𝑐  ↔  ω  ≼  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) ) | 
						
							| 24 |  | xpeq12 | ⊢ ( ( 𝑐  =  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ∧  𝑐  =  ( ( har ‘ 𝑎 )  ∪  𝑎 ) )  →  ( 𝑐  ×  𝑐 )  =  ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ×  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) ) | 
						
							| 25 | 24 | anidms | ⊢ ( 𝑐  =  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  ( 𝑐  ×  𝑐 )  =  ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ×  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) ) | 
						
							| 26 |  | id | ⊢ ( 𝑐  =  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  𝑐  =  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) | 
						
							| 27 | 25 26 | breq12d | ⊢ ( 𝑐  =  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  ( ( 𝑐  ×  𝑐 )  ≈  𝑐  ↔  ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ×  ( ( har ‘ 𝑎 )  ∪  𝑎 ) )  ≈  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) ) | 
						
							| 28 | 23 27 | imbi12d | ⊢ ( 𝑐  =  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  ( ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  ↔  ( ω  ≼  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ×  ( ( har ‘ 𝑎 )  ∪  𝑎 ) )  ≈  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) ) ) | 
						
							| 29 | 16 28 | spcv | ⊢ ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  →  ( ω  ≼  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ×  ( ( har ‘ 𝑎 )  ∪  𝑎 ) )  ≈  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) ) | 
						
							| 30 | 22 29 | syl5 | ⊢ ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  →  ( ¬  𝑎  ∈  Fin  →  ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ×  ( ( har ‘ 𝑎 )  ∪  𝑎 ) )  ≈  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) ) | 
						
							| 31 | 30 | imp | ⊢ ( ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  ∧  ¬  𝑎  ∈  Fin )  →  ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ×  ( ( har ‘ 𝑎 )  ∪  𝑎 ) )  ≈  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) | 
						
							| 32 |  | harndom | ⊢ ¬  ( har ‘ 𝑎 )  ≼  𝑎 | 
						
							| 33 |  | ssdomg | ⊢ ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ∈  V  →  ( ( har ‘ 𝑎 )  ⊆  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  ( har ‘ 𝑎 )  ≼  ( ( har ‘ 𝑎 )  ∪  𝑎 ) ) ) | 
						
							| 34 | 16 19 33 | mp2 | ⊢ ( har ‘ 𝑎 )  ≼  ( ( har ‘ 𝑎 )  ∪  𝑎 ) | 
						
							| 35 |  | domtr | ⊢ ( ( ( har ‘ 𝑎 )  ≼  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ∧  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼  𝑎 )  →  ( har ‘ 𝑎 )  ≼  𝑎 ) | 
						
							| 36 | 34 35 | mpan | ⊢ ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼  𝑎  →  ( har ‘ 𝑎 )  ≼  𝑎 ) | 
						
							| 37 | 32 36 | mto | ⊢ ¬  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼  𝑎 | 
						
							| 38 |  | unxpwdom2 | ⊢ ( ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ×  ( ( har ‘ 𝑎 )  ∪  𝑎 ) )  ≈  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼*  ( har ‘ 𝑎 )  ∨  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼  𝑎 ) ) | 
						
							| 39 |  | orel2 | ⊢ ( ¬  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼  𝑎  →  ( ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼*  ( har ‘ 𝑎 )  ∨  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼  𝑎 )  →  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼*  ( har ‘ 𝑎 ) ) ) | 
						
							| 40 | 37 38 39 | mpsyl | ⊢ ( ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ×  ( ( har ‘ 𝑎 )  ∪  𝑎 ) )  ≈  ( ( har ‘ 𝑎 )  ∪  𝑎 )  →  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼*  ( har ‘ 𝑎 ) ) | 
						
							| 41 | 31 40 | syl | ⊢ ( ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  ∧  ¬  𝑎  ∈  Fin )  →  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼*  ( har ‘ 𝑎 ) ) | 
						
							| 42 |  | wdomnumr | ⊢ ( ( har ‘ 𝑎 )  ∈  dom  card  →  ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼*  ( har ‘ 𝑎 )  ↔  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼  ( har ‘ 𝑎 ) ) ) | 
						
							| 43 | 13 42 | ax-mp | ⊢ ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼*  ( har ‘ 𝑎 )  ↔  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼  ( har ‘ 𝑎 ) ) | 
						
							| 44 | 41 43 | sylib | ⊢ ( ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  ∧  ¬  𝑎  ∈  Fin )  →  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼  ( har ‘ 𝑎 ) ) | 
						
							| 45 |  | numdom | ⊢ ( ( ( har ‘ 𝑎 )  ∈  dom  card  ∧  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ≼  ( har ‘ 𝑎 ) )  →  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ∈  dom  card ) | 
						
							| 46 | 13 44 45 | sylancr | ⊢ ( ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  ∧  ¬  𝑎  ∈  Fin )  →  ( ( har ‘ 𝑎 )  ∪  𝑎 )  ∈  dom  card ) | 
						
							| 47 |  | ssun2 | ⊢ 𝑎  ⊆  ( ( har ‘ 𝑎 )  ∪  𝑎 ) | 
						
							| 48 |  | ssnum | ⊢ ( ( ( ( har ‘ 𝑎 )  ∪  𝑎 )  ∈  dom  card  ∧  𝑎  ⊆  ( ( har ‘ 𝑎 )  ∪  𝑎 ) )  →  𝑎  ∈  dom  card ) | 
						
							| 49 | 46 47 48 | sylancl | ⊢ ( ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  ∧  ¬  𝑎  ∈  Fin )  →  𝑎  ∈  dom  card ) | 
						
							| 50 | 10 49 | pm2.61dan | ⊢ ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  →  𝑎  ∈  dom  card ) | 
						
							| 51 | 50 | alrimiv | ⊢ ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  →  ∀ 𝑎 𝑎  ∈  dom  card ) | 
						
							| 52 |  | eqv | ⊢ ( dom  card  =  V  ↔  ∀ 𝑎 𝑎  ∈  dom  card ) | 
						
							| 53 | 51 52 | sylibr | ⊢ ( ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 )  →  dom  card  =  V ) | 
						
							| 54 | 8 53 | impbii | ⊢ ( dom  card  =  V  ↔  ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 ) ) | 
						
							| 55 | 1 54 | bitri | ⊢ ( CHOICE  ↔  ∀ 𝑐 ( ω  ≼  𝑐  →  ( 𝑐  ×  𝑐 )  ≈  𝑐 ) ) |