1. If anything is certain, it is that I myself am not a Marxist.
[In a letter about the peculiar 'Marxism' which arose in France 1882]
2. As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.
3. Although our intellect always longs for clarity and certainty, our nature often finds uncertainty fascinating.
4. If there's one thing that's certain in business, it's uncertainty.