"The Christian does indeed live still in this world. It is a travesty on this Pauline doctrine when it is held to mean that when he escapes, inwardly, from the present evil world by the redeeming work of Christ the Christian can calmly leave the world to its fate. On the conrary, Christian men, even after they have been redeemed, are left in this world, and in this world they have an important duty to perform.In the first place, they do not stand alone, but are united in the great brotherhood of the Christian Church. Into that brotherhood it is their duty to invite other men by the preaching of the gospel; and they should pray that that preaching, through the supernatural operation of the Holy Spirit in the new birth, may be efficacious, and that the great brotherhood may expand yet more and more.In the second place, Christians should by no means adopt a negative attitude toward art, government, science, literature, and the other achievements of mankind, but should consecrate these things to the service of God. The separateness of the Christian from the world is not to be manifested, as so many seem to think that it should be manifested, by the presentation to God of only an impoverished man; but it is to be manifested by the presentation to God of all man's God-given powers developed to the full. That is the higher Christain humanism, a humanism based not upon human pride but upon the solid foundation of the grace of God. But these considerations do not make any less radical the step of which Paul speaks. It remains true that the Christian has escaped from this present age - from this present world with all its sin and all its pride. The Christian continues to live in the world, but he lives in it as its master and not as its slave. He can move the world because at last he has a place to stand."
- J. Gresham Machen, Machen's Notes on Galatians, ed. John H. Skilton (Philadelphia: Presbyterian and Reformed Publishing Company, 1972), 32-33.