"Let us return to our initial problem. We may begin by asking why we assume that someone being paid to do nothing should consider himself fortunate. What is the basis of that theory of human nature from which this follows? The obvious place to look is at economic theory, which has turned this kind of thought into a science. According to classical economic theory, homo oeconomicus, or "economic man"--that is, the model human being that lies behind every prediction made by the discipline--is assumed to be motivated above all by a calculus of costs and benefits. All the mathematical equations by which economists bedazzle their clients, or the public, are founded on one simple assumption: that everyone, left to his own devices, will choose the course of action that provides the most of what he wants for the least expenditure of resources and effort. It is the simplicity of the formula that makes the equations possible: if one were to admit that humans have complicated motivations, there would be too many factors to take into account, it would be impossible to properly weight them, and predictions could not be made. Therefore, while an economist will say that while of course everyone is aware that human beings are not really selfish, calculating machines, assuming that they are makes it possible to explain a very large proportion of what humans do, and this proportion--and only this--is the subject matter of economic science."