James McNeill Whistler Quote
If the man who paints only the tree, or flower, or other surface he sees before him were an artist, the king of artists would be the photographer. It is for the artist to do something beyond this: in portrait painting to put on canvas something more than the face the model wears for that one day: to paint the man, in short, as well as his features; in arrangement of colours to treat a flower as his key, not as his model. This is now understood indifferently well – at least by dressmakers. In every costume you see attention is paid to the key-note of colour which runs through the composition, as the chant of the Anabaptists through the 'Prophète', or the Hugenots' hymn in the opera of that name.
In a letter to 'The World', London 22 Mai, 1878; as quoted in Letters of the great artists – from Blake to Pollock, Richard Friedenthal, Thames and Hudson, London, 1963, p. 186