Decision-thinking is not unlike poker—it often matters not only what you think, but also what others think you think and what you think they think you think: The mental process (过程) is similar. Naturally, this card game has often been of considerable interest to people who are, by any standards, good thinkers. The great mathematician John yon Neumann was one of the founders of game theory. In particular, he showed that all games fall into two classes: there are what he called games of 'perfect information', games like chess where the players can't hide anything or play tricks: they don't win by chance, but by means of logic and skills. Then there are games of 'imperfect information', like poker, in which it is impossible to know in advance that one course of action is better than another. One mistaken idea about business is that it can be treated as a game of perfect information. Quite the reverse, business, politics, life itself are games which we must normally play with very imperfect information. Business decision are often made with many unknown and unknowable factors(因素)which would even puzzle(困惑)best poker players. But few business people find it comfortable to admit that they are taking a chance, and many still prefer to believe that they are playing chess, not poker. The subject discussed in this text is ______.