at given or expected prices they can sell their output as much as they want. 5 Once they have such confidence, they certainly need not concern themselves with the ordering of their activities However an agent who reveals such a fully confidence within an uncertain economy can hardly be regarded as rational or intelligent, whether he is selfish(reflected by his optimization process) I thus argue that the expected sale cannot be determined only by price information. N must contain quantity information. The following, which I believe to be very common in practice, is my own suggestion Information Used for Expectation For consumers. working contracts tenures. etc Fo f information takes the form of contracts, orders, etc, the expect ation function is very easy to define. What is said in contracts (or orders) is exactly what is expected. If information comes from past sale, the expectation function will depend on the pattern by which agents form their expectation. The models of adaptive expectation, learning and even rational expectation might be applied here, but the information, from which the expectation is derived, should also contain the quantity(the past sale) Demand Determination, a Backward Exposition. We are now ready for my backward exposition of the way demand is determined. It seems that the best way to do this is to put forward a set of questions to a series of agents s. "the output as much as they want"is certa inly referred to the optimum output derived from the agents optimization process given the expected prices 6. Else where( Gong, 1993, 1994b), I call such a revealed behavior as"full-confidence expectation"with its meaning and relation to the neoclasical system explained in detail8 at given or expected prices they can sell their output as much as they want.5 Once they have such confidence, they certainly need not concern themselves with the ordering of their activities. However an agent who reveals such a fully confidence within an uncertain economy can hardly be regarded as rational or intelligent, whether he is selfish (reflected by his optimization process) or not.6 I thus argue that the expected sale cannot be determined only by price information. N must contain quantity information. The following, which I believe to be very common in practice, is my own suggestion. Information Used for Expectation For consumers: working contracts, oral promises tenures, etc. For producers: orders past sales. If information takes the form of contracts, orders, etc., the expectation function is very easy to define. What is said in contracts (or orders) is exactly what is expected. If information comes from past sale, the expectation function will depend on the pattern by which agents form their expectation. The models of adaptive expectation, learning and even rational expectation might be applied here, but the information, from which the expectation is derived, should also contain the quantity (the past sale). Demand Determination, a Backward Exposition. We are now ready for my backward exposition of the way demand is determined. It seems that the best way to do this is to put forward a set of questions to a series of agents. 5 . "the output as much as they want" is certainly referred to the optimum output derived from the agents' optimization process given the expected prices. 6 . Elsewhere (Gong, 1993, 1994b), I call such a revealed behavior as "full-confidence expectation" with its meaning and relation to the neoclasical system explained in detail