Christianity differs from liberalism, then, in the first place, in its conception of God. But it also differs in its conception of man. Modern liberalism has lost all sense of the gulf that separates the creature from the Creator; its doctrine of man follows naturally from its doctrine of God. But it is not only the creature limitations of mankind which are denied. Even more important is another difference. According to the Bible, man is a sinner under the just condemnation of God; according to modern liberalism, there is really no such thing as sin. At the very root of the modern liberal movement is the loss of the consciousness of sin.

The consciousness of sin was formerly the starting-point of all preaching; but today it is gone. Characteristic of the modern age, above all else, is a supreme confidence in human goodness; the religious literature of the day is redolent of that confidence. Get beneath the rough exterior of men, we are told, and we shall discover enough self-sacrifice to found upon it the hope of society; the world’s evil, it is said, can be overcome with the world’s good; no help is needed from outside the world.

–J. Gresham Machen, Christianity and Liberalism (1923).