“It is clear then that?.?.?.?those states in which the middle element is large, and stronger if possible than the other two [wealthy and poor] together, or at any rate stronger than either of them alone, have every chance of having a well-run constitution.” Thus did Aristotle summarise his analysis of the Greek city states. The stability of what we would now call “constitutional democracy” depended on the size of its middle class. It is no accident that the US and UK, long-stable democracies today succumbing to demagogy, are the most unequal of the western high-income countries. Aristotle, we are learning, was right. (See charts.)
“倘使中產階級的人數超過其它兩個部分（富裕階級和貧窮階級）之和，或僅僅超過兩者之一，就可能建立一個持久的共和政體。”這是亞里士多德(Aristotle)分析希臘城邦國家之后得出的結論。我們現在所稱的“憲政民主政體”的穩定性取決于其中產階級的人數。并非巧合的是，美國和英國是西方高收入國家里最不平等的兩個國家；二者都是長期穩定的民主國家，現在卻被煽動性言論擺布。我們正在意識到，亞里士多德是對的。（參見圖表）