Theological liberalism, sometimes known as Protestant Liberalism, is a theological movement rooted in the early 19th century German Enlightenment, notably in the philosophy of Immanuel Kant and the religious views of Friedrich Schleiermacher. It is an attempt to incorporate modern thinking and developments, especially in the sciences, into the Christian faith. Liberalism tends to emphasize ethics over doctrine and experience over Scriptural authority. While essentially a 19th century movement, theological liberalism came to dominate the American mainline churches in the early 20th century. Liberal Christian scholars embraced and encouraged the higher biblical criticism of modern Biblical scholarship.
Protestant liberal thought in its most traditional incarnations emphasized the universal Fatherhood of God, the brotherhood of man, the infinite value of the human soul, the example of Jesus, and the establishment of the moral-ethical Kingdom of God on Earth. It has often been relativistic, pluralistic, and non-doctrinal.
Liberalism birthed other movements with varying emphases. Among these movements have been the Social Gospel, theological Feminism, Liberation theology, Process theology, and the Jesus Seminar. One product of these movements is the heretical Myth of Christian Origins which denies the divinity of Christ and the authority of scripture.
Reactions to theological liberalism
Various movements in Christianity resulted as reactions to liberal influence. Most of these groups attempted to reclaim and affirm what they viewed as traditional Christian orthodoxy. Reactions against liberalism have included:
- Evangelicalism, a conservative renewal movement of the 18th and 19th centuries, re-affirmed in the mid 20th century as separate from today's more narrowly defined "fundamentalism."
- Fundamentalism, an early 20th century movement within Evangelicalism in reaction to Liberalism and Modernism, has become more narrowly associated with dispensational theology and social separatism.
- Neo-Orthodoxy, an early-to-mid 20th century movement led primarily by Karl Barth and Emil Brunner which made use of existentialism and emphasized the transcendence of God and the sinfulness of humankind.
- Pentecostalism, an early 20th century movement which reacted against what some perceived as the stale worship and devotional life among churches dominated by liberalism.
- Neo-Wesleyanism, a mid-late 20th century movement in Methodism dominated by Albert C. Outler which developed authoritative editions of the works of John Wesley in an attempt to reclaim pure Wesleyan thought.
- Post-Liberalism, also called narrative theology, a late 20th century movement led initially by George Lindbeck which emphasizes the authority of the Biblical narrative as opposed to its historical veracity or inerrancy.
Other important liberal theologians include:
- George W. F. Hegel
- Albrecht Ritschl
- Adolph von Harnack
- Harry Emerson Fosdick, pastor of Riverside Church in New York City, perhaps liberalism's best known preacher
- Paul Tillich (referred to by Stanley Hauerwas and William Willimon in their 1989 book Resident Aliens as the last great 19th century theologian due to his substantial influence, not necessarily for his theology)
Liberalism has proven to be extremely controversial in the Church. While it had come to dominate the American religious landscape by the mid-20th century, by the end of the century it was dying as it suffered defeats in mainline churches and as American Christianity began placing a renewed emphasis on doctrinal orthodoxy.
- "No, I'm delighted that liberal theologians do their best to do what Pio Nono said shouldn't be done -- try to accommodate Christianity to modern science, modern culture, and democratic society. If I were a fundamentalist Christian, I'd be appalled by the wishy-washiness of their version of the Christian faith. But since I am a non-believer who is frightened of the barbarity of many fundamentalist Christians (e.g., their homophobia), I welcome theological liberalism. Maybe liberal theologians will eventually produce a version of Christianity so wishy-washy that nobody will be interested in being a Christian any more. If so, something will have been lost, but probably more will have been gained." - Richard Rorty, a postmodern philosopher 
- J. Gresham Machen, Christianity and Liberalism. Eerdmans, 1923; reprint 1990.