西方自由主義(liberalism)主要探討的主題，便是個人如何在社會中得到充分得自由。本文的「轉化」(transformation)研究，主要是指19世紀中葉英國自由主義在穆勒(John Stuart Mill)身上，從「古典的自由主義」(classical liberalism)「轉化」為「現代或修正的自由主義」(modern or revisionist liberalism)。而「轉化」的關鍵主要在於，以往「古典自由主義」強調個人自由的維護，對政政行動予以極大的限制，而新的自由主義，也就是在穆勒學說中逐漸突顯的「現代或修正的自由主義」，則把重點轉移為強調政府的積極功能。穆勒對古典自由主義的貢獻，主要在於他開拓了古典自由主義的新視野，除了經濟自由外，更重要的是個人自由。這使得古典自由主義跳脫中產階級的包袱後，依舊保持著歷久彌新的永�睇靋�；另一方面穆勒了解單是拓深古典自由主義的內涵，並不能解決當時代的問題，因此穆勒賦與政府必然機能的合法性之角色，這使得他開啟了現代自由主義的大門。但是，我們須注意的是，穆勒的現代自由主義是在古典自由主義的基礎上前進，也就是政府行動是以不違反個人自由為原則下進行的。

　　　　　The controversial principal subject of western liberalism lies in how a person gets the sufficient freedom in society. The research of “transformation” in this article indicates the process of John Stuart Mill’s liberalistic transformation, from “classical liberalism” to “modern or revisionist Liberalism”, whose truing point of transformation consists in the fact that the past “classical liberalism” has much emphasized protecting the personal freedom against the governmental action, but the new liberalism, to wit the modern or revisionist liberalism in Mill’s theory gradually outstanding, stresses the governmental active function. Mill’s contribytion to classical liberalism capitally means his enlarging the new domain of classical liberalism, including the more important personal freedom besides economic freedom, that results in the fact that classical liberalism remains the unshakable esteem of eternity, having escaped from the loading of the middle class; on another side Mill realizes that it is impossible to resolve the contemporary problems only to deepen the connotation of classical liberalism. As a result Mill endows the government with the legalization of the necessary function, which helps him enter into the field of modern liberalism. But we have to notice that Mill’s modern liberalism prevails on the basis of classical liberalism, as means that the governmental policy is put into action without disobeying the personal freedom.