The security dilemma is a fundamental feature of international politics, as states' efforts to increase their own security often decrease the security of others.

如果中原真的能消除战乱，我们两个老头子又何妨老死在戍边之地。

每一本书都是一次旅程，每一次旅程都是一本书。

孔子说：“将知识默记在心，学习时，不感到满足；教人时，不感到疲倦，对我来说没什么问题。”