Description: Reverse closure for an initial object: If a class has an initial object, the class is a category. (Contributed by AV, 4-Apr-2020)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | initorcl | |- ( I e. ( InitO ` C ) -> C e. Cat ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df-inito | |- InitO = ( c e. Cat |-> { a e. ( Base ` c ) | A. b e. ( Base ` c ) E! h h e. ( a ( Hom ` c ) b ) } ) |
|
| 2 | 1 | mptrcl | |- ( I e. ( InitO ` C ) -> C e. Cat ) |