以下是引用yxue122在2005-9-26 11:04:13的发言: 大家的推理都是建立在理性的基础上
还有一种情况就是卖莲蓬的人非理性,呵呵,即也许仅仅看楼主不顺眼

Suppose we know someone's objective and also know that half the time that person correctly figures out how to achieve it and half the time acts at random. Since there is generally only one right way of doing things (or perhaps a few) but very many wrong ways, the "rational" behavior can be predicted but the "irrational" behavior cannot. If we predict this person's behavior on the assumption that he is rational, we will be right half the time. If we assume he is irrational, we will almost never be right, since we still have to guess which irrational thing he will do. We are better off assuming he is rational and recognizing that we will sometimes be wrong. To put the argument more generally, the tendency to be rational is the consistent (and hence predictable) element in human behavior. The only alternative to assuming rationality (other than giving up and concluding that human behavior cannot be understood and predicted) would be a theory of irrational behavior--a theory that told us not only that someone would not always do the rational thing but also which particular irrational thing he would do. So far as I know, no satisfactory theory of that sort exists.
Insofar as the irrational part of their behavior is random, its effects are likely to average out in the aggregate.A second reason why the assumption works better than one might expect is that we are often dealing not with a random set of people but with people who have been selected for the particular role they are playing.