Nobody outside of a baby carriage or a Judge's chamber can believe in an unprejudiced point of view but, simply in self-interest, the biographer must try for one, or make us believe he has, or tell us that he hasn't.
Source, in full
"Love Letters, Some Not So Loving" (a review of H.G. Wells and Rebecca West by Gordon N. Ray), in The New York Times (13 October 1974); this has often been paraphrased as "Nobody outside of a baby carriage or a Judge's chamber believes in an unprejudiced point of view."