I have recently been re-reading J. Gresham Machen's Christianity & Liberalism, which was published just over a century ago in 1923. Many Christians are familiar with Machen's role in the fight against modernism in the church during the Fundamentalist--Modernist controversy. Many are also aware that Machen's criticism of liberalism was that it is not merely a distortion of the Christian religion but a different religion altogether.
The bulk of Machen's book is focused on the key doctrines of the Christian faith, showing the way that liberalism replaces those doctrines with those of its own invention. Near the end of the book, however, Machen discusses a topic that is a perennial issue among conservative Christians as well as liberals - the transformation of culture. Machen argues that Christians and liberals have very different views on this topic. Essentially, it boils down to the manner in which culture can be transformed.
Machen argues that "the true transformation of society will come by the influence of those who have themselves been redeemed" (p. 158). This means that "a blessed society cannot be formed out of men who are still under the curse of sin" (p. 158). The point is that the culture changes only when the hearts of those who are a part of the culture change, and the hearts of those who are a part of the culture can only be truly changed through the supernatural work of redemption.
A difference between Christians and liberals on this point is reflected in the different message of each. Machen explains:
The missionary of liberalism seeks to spread the blessings of Christian civilization (whatever that may be), and is not particularly interested in leading individuals to relinquish their pagan beliefs. The Christian missionary, on the other hand, regards satisfaction with a mere influence of Christian civilization as a hindrance rather than a help; his chief business, he believes, is the saving of souls, and souls are saved not by the mere ethical principles of Jesus but by His redemptive work (p. 156).
In other words, the Christian missionary is focused on preaching Jesus Christ and Him crucified, and it is only when God saves those who hear and believe this Gospel that a culture can truly change. The liberal missionary, on the other hand focuses on externals. Liberals prioritize a political and cultural message over the Gospel message. This is why liberalism in the late 19th and early 20th century adopted a social gospel. Thoughtful readers of Machen will understand that conservatives too have to be careful that they too do not replace the biblical gospel with a social gospel.
An equally important point that Machen makes is that seeking first the Kingdom of God and His righteousness is an end in itself. If we treat it as a means to an end such as cultural transformation, we have missed the point. As Machen explains it:
Our Lord said: "Seek ye first the Kingdom of God and His righteousness, and all these things shall be added unto you. But if you seek first the Kingdom of God and His righteousness in order that all those other things may be added unto you, you will miss both those other things and the Kingdom of God as well (p. 152).
Machen witnessed with his own eyes the destructive effects of liberalism in the church of his day. Conservatives who side with Machen know too well the danger of liberal doctrines of Scripture and God and salvation. But conservatives need to be aware that liberalism can slip in the back door of the church in other ways. Machen's words on this issue are words that all Christians should reflect on, especially in a day and age when so many evangelical Christians are tempted to prioritize penultimate things over ultimate things.