自由主義作為西方政治文明的成果，在西方近現代史上有著極為廣泛的影響，而現代自由主義是在傳統自由主義理論的基礎上形成和發展起來的嶄新的政治哲學思想。美國自由主義之本質乃是紮根於18世紀啟蒙運動之政治思想體系，傳統上自由主義信奉個人自由、機會平等、自由市場經濟、擴張定義的財產權、自由民主之資本主義以及有限政府。唯自19世紀末起，在經歷了一重新定義過程之後，傳統之美國自由主義漸漸為其「現代」版本所取代。本文透過對現代自由主義的形成和發展過程的認識，概略地闡述現代兩種自由主義的一些基本觀點和思想，以期對現代自由主義思想有一個正確的完整的認識。

As the fruits of western political civilization, liberalism has great influence in the western modern history, while the modern liberalism is a brand-new political philosophy which formed and developed on the basis of the traditional liberalism.The essence of liberalism in the United States of America, which took root in the 18th century Enlightenment political ideologies and traditionally espoused individual liberty, equality of opportunity, a free market economy, an expansive definition of property rights, liberal democratic capitalism, and limited government, has undergone a redefining process since the late nineteenth century and been replaced by a "modern" version, which emphasizes more equitable economic distribution by means of authoritative measures and social welfare.The article elaborates some basic points and thoughts of modern liberalism so as to have a complete understanding of the political thoughts of modern liberalism.