直觀來說, 連續性是講如果你改變某consumption good少許, 你對它的preference 不會有很大的改變
用sequential definition 的話: for any sequence {x_n} , {y_n} such that x_n is weakly preferred to y_n for all n , then x is weakly preferred to y, for x and y are limits of {x_n} and {y_n} respectively.
可以把sequence {x_n} 看成是我逐步(每一步就是一個n)的改變good x 少許, 同時又改變good y 少許( 就是sequential {y_n}啦), 如果preference 沒有重大改變的話, 在每一步, 如果 x_n is weakly preferred to y_n, 那在limit , 仍有 x is weakly preferred to y.
但是preference 因該物品該變少許而又大變化的話(non-continuous), 那雖然x_n is weakly preferred to y_n for all n, 但因有大變化, 可能使得你突然很討厭good x, 於是y is strictly preferred to x, 這樣preference 就違返continuity 了
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