本文主要以統治學意義上的「勢」論為中心，探討「勢」概念在戰國時代的發展情形，並從「相對關係」的角度分析其哲學義涵。筆者首先以《孟子》、《莊子》、《戰國策》為主要依據，考察「勢」概念義涵在戰國中後期所呈現的全面性發展，其中以統治學上的「勢」論最為興盛。而代表儒家的《孟子》及代表道家的《莊子》對這即將成為主流思潮的法家之「勢」（權勢、威勢、勢位）主張，則顯現相當程度的反對。
　　《荀子》書中有許多「勢」論。荀子除了擅長以「勢」表達各種層面的概念之外，對法家君王之「勢」主張則有矛盾之立論﹔而將君王之「勢」提昇到理論層次，更使《荀子》在法家「勢」論發展過程中，具有里程碑的意義。
　　《韓非子》書中除了眾所周知的一般性的「勢」治論之外，〈難勢〉篇特別值得吾人注意。筆者從篇中「隱括之法」、「度量之數」、「良馬固車，五十里而一置」等譬喻，嘗試釐清所謂的「人設之勢」應為「制度」之義，希望能闡明〈難勢〉篇的真諦。
　　最後，本文從「相對關係」的角度分析戰國時代「勢」概念所蘊涵的時間觀與空間觀。結論是：戰國時期的知識階層對「空間之勢」（包括大自然現象與人類社會之空間結構）的認知與操控，都勝過對「時間之勢」的了解與掌握。

　This paper discusses the development of the notion of Shi 勢 in the Warring States period and its philosophical implications in terms of relativity. I argue that Shi as a notion of governance became well developed between the 5th and 3rd centuries B.C. However, the Confucian philosopher Mencius and the Taoist philosopher Zhuangzi both refused to concur with the dominant current of thought, which emphasized the importance of Shi.
　Xunzi, who theorized about Shi on various levels, held some contradictory opinions toward the Shi of a king . Hanfeizi developed a new notion of "man-made Shi" (人設之勢) that denoted political institutions designed by man.
　This article concludes that the notion of Shi in the Warring States period comprises views of both "time" and "space." However, the majority of thinkers in this period devoted much more attention to the aspect of "space" than to "time."