There is one quality I find in all the artists I admire most – men like Masaccio, Michelangelo, Rembrandt, Cézanne. I mean a disturbing element, a distortion, giving evidence of a struggle of some sort... Great Art is not Perfect. Here the disturbing element comes in. It is instructive to know that Rembrandt copied Mantegna, whose art is the extreme opposite of his own. Why did he do so? Because he was conscious that his own art lacked the classical element. He was aware of the opposite, and that makes him greater.

Quote in 'Conversations with Henri Moore', J.P. Hodin, in 'The Observer', 24 November 1958