The chief characteristics of original Protestantism were the acceptance of the Bible as the only source of infallible revealed truth, the belief in the universal priesthood of all believers, and the doctrine that a Christian is justified in his relationship to God by faith alone, not by good works or dispensations of the church. There was a tendency to minimize liturgy and to stress preaching by the ministry and the reading of the Bible. Although Protestants rejected asceticism, an elevated standard of personal morality was advanced; in some sects, notably Puritanism, a high degree of austerity was reached. Their ecclesiastical polity, principally in such forms as episcopacy (government by bishops), Congregationalism, or Presbyterianism, was looked upon by Protestants as a return to the early Christianity described in the New Testament.
Protestantism saw many theological developments, particularly after the 18th cent. Under the influence of romanticism, which stressed the subjective element in religion rather than the revelation of the Bible, the formal systems of early Protestant theology began to dissolve; this doctrine was best expressed by Friedrich Schleiermacher, who placed religious feeling at the center of Christian life. Along with this came the assertion that the fatherhood of God and the unity of humanity were the basic themes of Christianity. Later there was a neoorthodox movement, which, under the leadership of Karl Barth and Reinhold Niebuhr, sought a return to a theology of revelation; a new school of Bible interpretation as expressed in the work of Rudolf Bultmann; and a theology, derived in part from existentialism, developed by Paul Tillich.
In the United States, four broad theological positions cut across denominational lines: fundamentalism, which stems from the antitheological periods of revivalism in the 18th and 19th cent. (see Great Awakening) and adheres to a literal interpretation of the Bible and a pietistic morality; liberalism, the heir to the Social Gospel movement, which encourages freer interpretation of theological doctrines and emphasizes church responsibility for social justice; Pentecostalism, which emphasizes ecstatic religious experience especially as communicated through the gifts of the Spirit; and the neoorthodoxy of Reinhold Niebuhr and Karl Barth.