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Protestantism, the religious background associated with Rehnquist, encompasses a diverse group of Christian denominations that emerged from the Protestant Reformation in the 16th century. It includes prominent branches like Lutheranism, Anglicanism, Calvinism, and various evangelical traditions. Protestantism emphasizes the importance of personal faith, individual interpretation of the Bible, and the priesthood of all believers, guiding Rehnquist's perspective on legal and social issues throughout his career.