“However, he added, there is one big difference: "Our particles in economics are smart, whereas yours in physics are dumb." In physics, an elementary particle has no past, no experience, no goals, no hopes or fears about the future. It just is. That's why physicists can talk so freely about "universal laws": their particles respond to forces blindly, with absolute obedience. But in economics, said Arthur, "Our particles have to think ahead, and try to figure out how other particles might react if they were to undertake certain actions. Our particles have to act on the basis of expectations and strategies. And regardless of how you model that, that's what makes economics truly difficult.”