事势之流 相激使然

世事的变化趋势或态势是各种因素、力量相互碰撞、激发的结果。这是古代著名史家司马迁提出的历史命题。“事势”即世间之事的基本趋势和态势；“流”本指水流、河流，比喻事物的演变过程。司马迁认为，历史是人的故事，但并不以某个人或某些人的意志为转移；世事流转，最终呈现什么样态，取决于参与这一过程的各种因素或力量的相互碰撞或激发。其中蕴含历史合力论的思想。

The Flow of Events Is Caused by Interactions

Changes in trends or situations arise from the clashes and stimuli of factors and forces. This was an explanation of history proposed by the famous ancient Chinese historian Sima Qian. "Events" were the basic trends or situations in the world; their "flow" was how they changed over time like flowing rivers. Sima Qian felt that while history was composed of the stories of people, it could not be changed by the will of any single person or some persons. Rather, the outcome of the flow of events was basically determined by the clash or stimulus of various factors and forces involved in the process. This embodies ideas of the convergence and interaction of historical forces.

引例事势之流，相激使然，曷足怪焉？（《史记·平准书》）（世事的变化趋势或态势，是各种因素、力量相互碰撞、激发的结果，何足为奇？）

Changes in trends or situations are the result of the clashes and interactions between various factors and forces. What is so strange about that? (Records of the Historian)