多元主義係一種關於如何理解諸種價值和善的存在樣式與相互關係的認知態度，而其對立面則為一元論。一元論認為任何真正的問題必定存在著一個唯一正確的答案，而且這些正確的答案皆可調和在一個協同一致的體系之中。多元主義則主張群體生活裡的重要問題未必只有一個可供參考的答案，而且各種善和價值往往是不可共量的、相互衝突的，因此，一切美好事物、一切可欲的價值並無法被整合在一個協同一致的體系之中。本文的重點在於分析多元主義的重要代表人以賽亞．伯林的核心論點，以及他為了追溯多元主義的思想源頭而對馬基維利、維柯、赫德所進行的思想史考察。此外，本文也將探討多元主義對於當代的政治理論和民主過程所能給予的啟示。

As an antithesis of monism, pluralism insists that there are more than one answer to any genuine question and also contends that all the goods and objective values in human life cannot be harmonized into a unified and consistent system. On the contrary, the desirable goods are usually in conflict and are therefore incommensurable. This article investigates Isaiah Berlin’s enduring contributions to pluralist reasoning both as a political theorist and as a historian of ideas, and then analyses what pluralism can tell for political theory and modern democracy.