持盈守谦之术与两汉外戚之兴衰

《易经》中的“物极必反”之理强调“盛”与“衰”之间的相互转化，而《老子》，则单向侧重“由盛及衰”的一面。正是以此为理论基础，保身守国的“持盈守谦”之术产生了。两汉外戚作为整体的绵延不绝与作为个体的忽生忽灭的特点正好与上述观念 形成“同构”关系。

The Way of Stopping Before Overdoing it and the Rise-and-Fall of Waiqi in Han Dynasty

The way of stopping before overdoing it is a important living and political topic.It mainly comes from the I ching and Lao tzu.I ching thinks that things will develop in the opposite direction when they become extreme, but Lao tzu more emphasizes the change from rise to fall.Waiqi was an important political power all through Han dynasty,with its living character from rise to fall.So the article inquires into the relations between the two.