Goddess of Grammar
New member
There's no "best of one's capacities" in that sentence, there's a "he's the best judge"--so it means no one else can be as good.
If there was a "best of one's capacities" it would mean that he's doing the best he can--the phrasing might be "He judges himself to the best of his capacities". (I would prefer "to the best of his capacity".)
If there was a "best of one's capacities" it would mean that he's doing the best he can--the phrasing might be "He judges himself to the best of his capacities". (I would prefer "to the best of his capacity".)