“The lessons of mathematics are simple ones and there are no numbers in them: that there is structure in the world; that we can hope to understand some of it and not just gape at what our senses present to us; that our intuition is stronger with a formal exoskeleton than without one. And that mathematical certainity is one thing, the softer convictions we find attached to us in everyday life another, and we should keep track of the difference if we can.”