Harry Emerson Fosdick (1878-1969) popularized liberal theology in his preaching at the Riverside Church in New York City

Liberal theologians used insights and methods from the social sciences to shape Christian theology. Liberal theology has its roots in the Enlightenment, which emphasized free will, reason, and the ability of human beings to make progress in all things including religion; and also in romanticism which insisted on feeling and intuition as essential to human life. Friedrich Schleiermacher, the "father of liberal theology," identified religion as a feeling of absolute dependence. For him, theology described internal religious experience rather than defining external religious truth. D. F. Strauss wrote the Life of Jesus, which sought to separate the "historical" life of Jesus from the "myths" surrounding it. In the United States, William Ellery Channing was an exponent of liberalism, leading some Congregationalists into Unitarianism. Later in the nineteenth and twentieth centuries, biblical criticism would play a large role in liberal theology. A contrasting movement was confessionalism, which responded to modernity by asserting the external authority of Scripture and confessions.