The fireworks that exploded at Dayton, Tennessee, at the 1925 "Monkey Trial," were first lit two centuries earlier, though the fuse had smoldered quietly. In the 1700s, European intellectuals revamped the millennium-old system for discerning truth: instead of grounding all knowledge in biblical revelation, they tried to build on the foundation of human reason.

This "enlightened" method (thus the name for the period and movement, the Enlightenment) produced some startling conclusions. David Hume (d. 1776) reasoned that God's existence could not be "proved." Immanuel Kant (d. 1804) and Friedrich Schleiermacher (d. 1834) argued that religion was not so much about God as about people's religious experiences. G. W. F. Hegel (d. 1831) said God was not the personal being described in the Bible but an impersonal force.

The Enlightenment championed the scientific method, where everything—including the Bible—was subject to rational, empirical analysis. In this environment, the discipline of biblical criticism grew up. It was also the context in which Charles Darwin concluded the world wasn't created in six days but was the product of millions of years of evolution.

Such European developments made their way across the Atlantic only slowly, but by the end of the 1800s, many American thinkers had become Enlightenment rationalists, or "liberals" or "modernists." This development alarmed many American Christians.

Harold Carl, chaplain and lecturer in religion at Berry College, Mt. Berry, Georgia, here explains the distinctives of American liberalism, a movement that sparked what is now called the fundamentalist-modernist controversy.

"A God without wrath brought men without sin into a kingdom without judgment through the ministrations of a without a cross." So wrote neo-orthodox theologian H. Richard Niebuhr, criticizing the nineteenth-century liberal "gospel."

Even today's liberals recognize the truth in Niebuhr's jibe, and they reject a lot of nineteenth-century liberalism's easy rationalism. But these liberals were not trying to water down the gospel. Instead, they believed they were rescuing religion from doctrinal bondage and obscurity. They sincerely wanted to make Christianity palatable to modern people. Many were, in one sense, trying to make the faith user-friendly.

They did this by emphasizing a number of themes, which became distinctives of American liberalism.

A first-hand God

In the 1800s, conservative theologians tended to balance God's transcendence—that he is self-sufficient and apart from, far above, and infinitely greater than creation—with his immanence. Liberal theologians favored the immanence of God—the God "present to creation," active within the universe, involved in human history.

For William Adams Brown, one of America's "Christocentric liberals," God was "not a transcendent being living in a distant heaven whence from time to time he intervenes in the affairs of earth. He is an ever-present [spirit] guiding all that happens to a wise and holy end."

Friedrich Schleiermacher, German father of liberal theology, taught that people become one with God, not through the objective death and resurrection of Christ, but through a feeling of "absolute dependence" and "God consciousness."

Some liberals blurred the distinction between the Creator and the creation, between revealed religion and religious experience. God was experienced primarily in nature and human reason. American churchman Theodore Parker (d. 1860) wrote, "There is no difference but of words between revealed religion and natural religion, for all actual religion is revealed in us, or it could not be felt, and all revealed religion is natural or it would be of no use to us."

A reasonable faith

Liberalism exchanged the external authority of the Bible and the teachings of the church for the internal authority of reason.

Much of Scripture was viewed as poetic, mystical, even mythical. At best, it was a flawed human record of history, not a divine revelation—and it should be analyzed as one would analyze any book. Charles A. Briggs, in The Authority of Holy Scripture: An Inaugural Address  (1891), said,

"It is not a pleasant task to point out errors in the sacred Scripture. Nevertheless Historical Criticism finds them, and we must meet the issue whether they destroy the authority of the Bible or not."

Reason (along with feeling, as above) reigned as a final arbiter of truth. The first president of the Free Religious Association, Octavius Brooks Frothingham (d. 1895), wrote, "The new Liberal Church has a consistent scheme of thought; it goes to the mind for its ideas; it admits the claim of spontaneity; its method of obtaining truth is rational; the harmony it demands is harmony of principles—the orderly sequence of laws."

As a corollary, liberals assumed that reasonable, educated, modern people could not accept the miraculous. Liberals contended that biblical miracles were "pre-scientific" explanations of events people did not understand. The immanent God of liberalism did not interrupt the spontaneous course of nature and history but acted within nature and history. Theodore Parker wrote, "God, ever present, never intervenes; acting ever by law, a miracle becomes needless, and also impossible."

Hope for humanity

Liberals tended to emphasize human freedom and people's capacity for good. Humanity was moving forward and upward. God wasn't saving a sinful humanity; he was perfecting an incomplete and immature humanity. John Fiske (d. 1902), in The Destiny of Man, wrote, "The future is lighted for us with the radiant colors of hope. Strife and sorrow shall disappear. Peace and love shall reign supreme."

Thus morality was stressed more than doctrine. Walter Rauschenbusch (d. 1918), champion of the social gospel, argued that religion and ethics were inseparable and that "Ethical conduct is the supreme and sufficient religious act." Many liberals followed Kant in teaching that Jesus was merely the personified idea of good, an example to follow. The ethical teachings of Jesus were paramount.

Innate human depravity was thus denied. Rauschenbusch wrote, "The permanent vices and crimes of adults are not transmitted by heredity, but by being socialized . …Hereditary social evils are forced on the individual embedded in the womb of society." Sin was therefore a result of social forces.

Furthermore, it was considered mere error and limitation, which moral and ethical education would eliminate. "Education," German theologian G. E. Lessing (d. 1781) said, "is revelation that affects the individual … and the development of revealed truths into truths of reason is absolutely necessary if the human race is to be helped by them."

Evolutionary truth

Evolution became a flash point in 1920s America because it contained so many elements of liberal thought.

Evolution gave nineteenth-century liberals an earth that had developed over millions of years, not by the supernatural, outside intervention of God. Thus evolutionary thought encouraged the doctrine of divine immanence—God working in and through creation and history.

When the doctrine of evolution was applied to sociology, liberals concluded that humanity was not stuck in sin and depravity but was evolving gradually toward a greater good. John Fiske wrote, "The dream of poets, the lesson of priest and prophet, the inspiration of the great musician, is confirmed in the light of modern knowledge; as we gird ourselves up for the work of life, we may look forward to the time when in the truest sense the kingdoms of this world shall become the kingdom of Christ."

Thus, religious ideas became increasingly relative and subject to reason. Beliefs were said to undergo a long course of development, beginning with polytheism and moving to monotheism. Judaism progressed to Christianity. G. E. Lessing believed biblical revelation and historical truths are of a lower order than the "necessary truths of reason." The Old Testament was relevant for humankind in its infancy; the New Testament, its youth. Full-grown humanity must be ruled by reason.

The essential conflict over evolution is illustrated by the contrasting statements of two American theologians. Charles Hodge (d. 1878), conservative at Princeton Theological Seminary, wrote in What Is Darwinism? (1874),

"What is Darwinism? It is atheism … an absent God who does nothing is, to us, no God."

Fiske, for his part, said, "Evolution is God's way of doing things."

A new religion

Historian Sydney Ahlstrom described the nineteenth century as "The Golden Age of Liberalism." It made major inroads in Congregationalism, Methodism, Unitarianism, and in the Protestant Episcopal Church, and substantially influenced Baptist and Presbyterian denominations. Seminaries like Harvard, Yale, Union (New York), Andover, and Boston University gradually became centers for liberal thought, also called "the new theology" or "progressivism."

Some conservatives moderated their views in light of liberalism. Some, for example, believed God created the earth, though they acknowledged he may have taken millions of years to do it. Others distrusted some miracles (like Jonah and the fish) while fully accepting others (the Resurrection).

But many would not budge on any point. Presbyterian theologian J. Gresham Machen represented this group, which concluded that liberalism was not another form of Christianity but another religion all together. It is this group—the vocal and the intransigent—who began to publicly attack liberalism in the early 1900s and who eventually took on the name "fundamentalists."