‘Most things in the world are absolute in terms of taking someone’s word for it. For example, rulers. But if you yourself made a sphere, you could never know if it was one. That fascinates me. Nobody will know it. It cannot be proven, so long as you avoid instruments. If I made a sphere and asked you, “Is it a perfect sphere?” you would answer, “How should I know?” I could insist that it looks like a perfect sphere. But if you looked at it, after a while you would say, “ I think it’s a bit flat over here.” That’s what fascinates me – to make something I can never be sure of, and no one else can either. I will never know, and no one else will ever know.’ 

 William de Kooning, from an interview with Harold Rosenberg, first published in Art News, vol. 71, no. 5. September 1972, pp. 54 – 59