Thinking about the world can be a messy affair. You can do it with the right tools, which come with a warning. — Neats and Scruffies. The history of philosophy shows us two broad kinds of thinkers. And a few of a third. There are those who, like Plato, liked things neat, tidy, pristine. A place for everything, and everything in its place. And everyone, as becomes clear from his Republic. These philosophers’ ideal is mathematics…