The first amendment to the US Constitution states "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof" The two parts, known as the "establishment clause" and the "free exercise clause" respectively, form the textual basis for the Supreme Court's interpretations of the "separation of church and state" doctrine.
The First Congress' deliberations show that its understanding of the separation of church and state differed sharply from that of their contemporaries in Europe. As 19th century Union Theological Seminary historian Philip Schaff observed:
“The American separation of church and state rests upon respect for the church; the [European anticlerical] separation, on indifference and hatred of the church, and of religion itself…. The constitution did not create a nation, nor its religion and institutions. It found them already existing, and was framed for the purpose of protecting them under a republican form of government, in a rule of the people, by the people, and for the people.