本文以美國憲法第一修正案的宗教條款和聯邦最高法院的有關司法解釋作?分析對象。本文的目的是，介紹和分析美國憲法第一修正案對宗教的規定和美國聯邦最高法院關於憲法第一修正案中「宗教」一詞的解釋。?所周知，美國聯邦最高法院是唯一一個憲法解釋機構，因而憲法的法定解釋涉及兩個層次：憲法條文本身和聯邦最高法院對其之解釋。本文分?兩個部分：1. 分析憲法第一修正案的宗教條款本身所給出的宗教定義；2. 分析聯邦最高法院針對憲法第一修正案中「宗教」一詞所下的定義和解釋。本文指出，歷經一個多世紀的變遷後，從20世紀中葉開始，最高法院對第一修正案中「宗教」一詞的理解，已從傳統猶太─基督教的有神論過渡到包容其他宗教的多元主義。

This article aims at providing a preliminary analysis of the legal definition of religion in the First Amendment to the Constitution of the United States. As the Supreme Court, the court of the highest jurisdiction in the United States, is the only authority that interprets the Constitution, the task of this essay is twofold: a study of the religion clause in the First Amendment, and an analysis of the Supreme Court’s interpretation of the religion clause. By reviewing some selected cases, this article argues that the Supreme Court’s explication of the legal definition of religion in the First Amendment has gradually moved from an exclusivistic approach to an inclusivistic approach that embraces various kinds of religion that are heterogeneous to the traditional monotheistic Judeo-Christian religion.