Emanuel Derman on the difference between models and law:
In physics, Maxwell’s theory and quantum mechanics allow you to predict the way an electron spins about its own axis inside a hydrogen atom to an accuracy of twelve decimal places. Something that accurate isn’t just a model—it’s a law. In economics, by contrast, there are no laws at all, only models, and you’re immensely lucky if you can predict up from down.
Still curious? Read My Life as a Quant: Reflections on Physics and Finance.