Ah_sa:
问： 假设偏好具完备性是否合理？传递性又是否合理？
1、完备性: 对于任两个不同的选择（消费束），均可以比较。
2、传递性: 对于消费束A,B & C, 假如A比B好,B比C好,则A比C好
角雀:
我的观点：偏好具有完备性与传递性是合理并且正确的。不过个人对于物品的评价是随着自身条件及外部环境的改变而改变的。因自身条件及外部环境是不断改变的，人们对物品的评价也是不断改变的。所以在某个时点上进行静态分析，完备性与传递性导致的偏好次序是成立的，但是一旦条件与环境发生变化，这种次序就会被打乱，根据新的条件与环境形成新的次序。由于条件与环境的微小变化是不断发生的，偏好次序的微小调整也是不断发生的，这时若忽视了条件及环境的变化，就会以为偏好次序相近的两组偏好的次序是不确定的。若条件及环境发生大的变化，整个偏好次序就会有一些根本性的变化。
大笨蛋:
任选一个真实世界的横截面或纵截面，可以观察到人们都在做出各种各样的选择或者正针对着选择采取行动。而只要有选择，就说明（看不见的）偏好（表现为选择）是完备的，可以比较（取舍）的。因此可以说，在静态中（即约束条件不变）或动态中，偏好都是完备的。
在静态中，偏好的传递性或许能说得通；但在动态中，偏好就不一定是传递的。喜新厌旧就是一个很好的例子：昨天的你可能喜欢a而不是b，但今天的你可能更喜欢b而非a了。
Ah_sa:
For comlpeteness, I'm not sure. It seems to me that, sometimes a person cannot make choice between two options that are too unfamiliar to him. For example, if you ask a person whether he wants to eat "1000 apples, 500 oranges and 700 eggs" or eat "800 apples, 800 oranges and 800 eggs", he may say, "I don't know, I haven't eaten so many stuff before". Similarly, if you ask whether a person wants a cup of tea or a piece of cake at 2:00pm on 11/12/2040, he may not be able to choose.
You may have encountered the following dilemma (just for fun):
If your mother and your lover both don't know swimming, but both fall into the sea. Now you can only save one of them, what will you do?
( If this question is raised by you mother or your lover alone, you definitely have an answer. If they ask you together, you're in trouble. )
大笨蛋:
上面的例子涉及到偏好的实证的问题。判定偏好的完备性只有在必须作出选择而且不能同时选择（或说消费）中才能进行。否则就没有意义。因为谁也不知道你心中的想法（包括你自己）。
假定a和b不能同时选择（例如一个人不能同时选择吃饭和睡觉 ），若某人说他对a和b无差异，这并不意味着a和b对他来说无差异的。只要他最终作出了选择，那么a和b对他来说就是有差异的。即a和b是“完备“的。如果他没有做出选择，那么也不能据此说a，b不可比较，因为他根本就没有选择。只有在选择中才能显示偏好。所谓实践是检验真理的标准，用在这里也是适合的。
Ah_sa:
Concerning transitivity, there is a famous problem of framing (包装) proposed by Kahneman and Tversky(1984):
(1) Suppose you have to buy a TV for $1000 and a cup for $10. The salesman tells you that the cup is onsale for $5 less (50% off) at the other branch of the store, located 20 minutes away. But the TV is the sa,e price there. Would you make the trip to the other store?
It turns out that the fraction of respondents saying that they would travel to the other store for the 5 dollar discount is much higher than the fraction who say they would travel when the question is changed so that the 5 dollar saving is on the TV. This is so even though the ultinate saving obtained by incurring the inconvenience of travel is the same in both cases.
(2) On the other hand, people are indifferent in the following situation:
Because of a stockout you must travel to the other store to get the two items, but you will receive 5 dollars off on either item as compensation. Do you care on which item this 5 dollar discount is given?
(3) The above experiment shows that many people violates transitivity. To see this, denote:
x: travel to the other store and get $5 discount on the cup.
y: travel to the other store and get $5 discount on the TV.
z: Buy both items at the first store.
Part (1) shows that x>y and y>z. Part (2) shows that x=y. Thus, violating transitivity!
coolfrank:
关于偏好的传递性是否成立，是有争论的，比如“孔多塞悖论”，具体内容大家可以参考马斯克莱尔的微观经济学。
zqdong:
也许现实中有与此假设不符的例子
但是为研究之便，有必要做这样的假设
金融杀手:
in fact,this is always right,but , it only can apply most conditons ,not all.it is just a asumption,
参见：http://bbs.efnchina.com/dispbbs.asp?boardID=92507&replyID=101500&ID=28252&skin=1
