James also uses the trope of the two selves: one is in society, the man everyone knows. The other, simultaneously, is in his room writing, like a phantom.
I forget the title of this short story, but I believe similar conceits recurs in several of them. His short-stories tend to be metafictional. [update: it is called "The Private Life."]
The creator puts the best of himself or herself in the work itself. A work can be perfect in a way that a human being never can. Such a form as Grecian goldsmiths make.
The biographer wants to drag the creator back into the muck.