The enemy is made the more dangerous because it is found within, rather than without, the Church. Definite opponents of the Christian religion could have been more easily met; but now as in ancient times Satan has preferred to labor for the most part in the dark. The change has come very quietly and very gradually. There have been few open breaks; there have been comparatively few open denials; good men, in their ignorance, have often become emissaries of unbelief. The Gospel has not been openly contradicted, but it has been quietly pushed aside. It has quietly faded away, as one picture fades away before another on the screen; and another gospel has assumed its place. Many men are quite unconscious of the change; they are made very angry by being told the truth. Others are not so completely blind; they know in their heart of hearts that all is not well. But they will do nothing unpleasant to preserve the purity of the Church; they preach the true Gospel themselves, they say, but let others in the same church preach what they will. God will ultimately honor the truth, they tell us; God will ultimately destroy error; but meanwhile let us above all have peace. Thus is Gamaliel cited as though he were a Christian saint; thus does a worldly urbanity masquerade under the name of love; thus has a polite optimism been substituted for the dread solemnity and exclusiveness of the Gospel of Christ.
J. Gresham Machen, “The Present Situation in the [Mainline] Presbyterian Church,” Christianity Today 1.1 (1930), 5.