Our world is a black box, predictable but not understandable

On good days, the world seems like a well-run railway: things happen according to principles, laws, rules and generalisations that we humans understand and can apply to particulars. We forgive the occasional late trains as exceptions that prove the rule. But other times we experience the world as a multi-car pile-up on a highway. The same laws of physics and of governments apply, but there are so many moving parts that we can't predict the next pile-up and we can't explain the details of this one – 'details' that can let one car escape with a bent fender while another erupts in a fireball. What's true of a car pile-up is also true of an uneventful autumn walk down a path arrayed with just exactly those leaves and no others.