J. Gresham Machen on Faith for Its Own SakeChristianity and Liberalism (Wm. B. Eerdmans: 1923), pp. 141-3.
… Faith is so very useful, they tell us, that we must not scrutinize its basis in truth. But, the great trouble is, such an avoidance of scrutiny itself involves the destruction of faith. For faith is essentially dogmatic. Despite all you can do, you cannot remove the element of intellectual assent from it. Faith is the opinion that some person will do something for you. If that person really will do that thing for you, then the faith is true. If he will not do it, then the faith is false. In the latter case, not all the benefits in the world will make the faith true. Though it has tranformed the world from darkness to light, though it has produced thousands of glrious healty lives, it remains a patholoical phenomenon. It is false, and sooner or later it is sure to be found out. ¶ Such conterfeits should be removed, not out of a love of destruction, but in order to leave room for the pure gold, the existence of which is implied in the presence of the counterfeits. Faith is often based upon error, but there would be no faith at all unless it were sometimes based upon truth. But if Christian faith is based upon truth, then it is not the faith which saves the Christian but the object of faith. And the object of the faith is Christ.