A great portrait is always more a portrait of the painter than of the painted. When we look at a portrait by Holbein or Rembrandt it is of Holbein or Rembrandt that we think more than of the subject of their picture. Even a portrait of Shakespeare by Holbein or Rembrandt could tell us very little about Shakespeare. It would, however, tell us a great deal about Holbein or Rembrandt.

— Samuel Butler, Notebooks, 1912