I began to understand my sensations, to know what I wanted, at around the age of forty.... but only vaguely. At fifty, that is in 1880, I formulated the idea of unity, without being able to render it. At sixty, I am beginning to see the possibility of rendering it.
(c. 1890); as quoted in Painting Outside the lines, Patterns of Creativity in Modern Art, David W. Galenson, Harvard University Press, 30 Jun 2009, p. 84