Machen wrote, “The liberal believes that applied Christianity is all there is of Christianity, Christianity being merely a way of life.” From Richard Gamble’s book The War for Righteousness:
From Princeton Theological Seminary in 1923, J. Gresham Machen fired another salvo at Protestant liberalism in his Christianity and Liberalism, which Walter Lippmann later called “the best popular argument produced by either side in the current controversy.” Machen acknowledged the dramatic changes that had swept the world in the past hundred years, and he agreed with the liberals’ assessment of the basic question facing Christianity in the contemporary world, namely, “What is the relation between Christianity and modern culture; may Christianity be maintained in a scientific age?” From this point on, however, he disagreed sharply with the progressive clergy. It was one thing to admit that the world was changing, but quite another to say that Christianity had to change along with it.
Machen proposed that liberalism had not rescued Christianity at all but rather had substituted something alien in its place. Liberalism had constructed an entirely new religion that diverged from the historic faith in every basic doctrine, from the nature of God and man, to the Bible, Christ, salvation, and the church. He rejected liberalism’s view of God’s immanence, its tendency to identify sin everywhere but within the human heart, and its fondness for statist collectivism. At the root of the problem he found liberalism’s penchant for making Christianity a means to another end, for putting “applied Christianity” above more fundamental concerns. He granted the need for Christian influence in the world but lamented that “the liberal believes that applied Christianity is all there is of Christianity, Christianity being merely a way of life.” Of its global aspirations, Machen complained that “the missionary of liberalism seeks to spread the blessings of Christian civilization (whatever that may be), and not particularly interested in leading individuals to relinquish their pagan beliefs.” At the heart of the debate was the definition of Christianity’s fundamental mission in the world.
From The War for Righteousness by Richard M. Gamble, pp. 249-250, ISI Books