Dirt Under The Rug

Like Paul, I have been thinking a lot about what makes a good model and what makes a bad one. In physics or even biology, theories can come pretty close to being indistinguishable from the real thing. (Tables ARE made of atoms. Avoid the temptation to think about this or you will lose your footing.) Models are different, and are by definition not the real thing. They are simplifications, more or less gross as the case may be. (Stock prices do NOT evolve lognormally).