Classic View : Say 's Law
法國經濟學者薩斯( Jean B. Say ,1767 - 1832 ),在1803年出版了《政治經濟學原理》。
當中提出了一個論點﹕「Should a trademand say, "I do not want other product for my woolens I want money,"
..."Your say, you only want money; I say, you want other commodities, and not money.
... Wherefore, it is products that you want, not money. "" (A Treatise on Political Economy, P133)。
交易的目的,人們最終是為了物品。人們提供物品於市場上,把它交換成金錢,再把金錢交換成自己想要的物品。