Van Gogh on how his art changed in Arles

From a letter dated April 9, 1888:

“I think that what Kahn says is perfectly true, that I haven’t taken tonal values into account enough, but they’ll be saying something very different later on—no less true. It’s impossible to deal with tonal values and colour. Th. Rousseau did it better than anyone else, but because of the mixing of the colours, the darkening with time has increased, and his pictures are now unrecognizable. One cannot be at the pole and the equator at the same time. One has to choose, which I hope I do, and it will probably be colour.”
 Subscribe to Praeterita in a reader