The question that gives us our title today comes from a classic Calvin & Hobbes cartoon: one of those that does NOT include the tiger at all. The cartoon consisted of a brief conversation between Calvin and his mother. Calvin wants a ride to the store. Mom says he is perfectly healthy and the weather is nice -- he can walk. She adds, "why do people have feet?" He responds, "to reach the gas pedal." There is a profound commentary about philosophy and teleology there somewhere, but I won't work so hard as to dig it out.