What's the difference between an economist and a physicist? It's not a joke but a distinction addressed by Emanuel Derman, who says the difference is that most economists have never really seen a successful model. Not knowing a good from a bad one they end up overly denigrating or deifying models. Derman considers the value of models and theories before concluding that: "The Wall Street people are going to reflexively overshoot and be too greedy. The Senate people are going to reflexively grandstand and be too uninformed and try to rein them in."