As a matter of fact, however, Paul did nothing of the kind; and only because he (and others) did nothing of the kind does the Christian Church exist today. Paul saw very clearly that the differences between the Judaizers and himself was the differences between two entirely distinct types of religion; it was the differences between a religion of merit and a religion of grace. If Christ provides only a part of our salvation, leaving us to provide the rest, then we are still hopeless under the load of sin. For no matter how small the gap which must be bridged before salvation can be attained, the awakened conscience sees clearly that our wretched attempt at goodness is insufficient even to bridge that gap. The guilty soul enters again into the hopeless reckoning with God, to determine whether we have really done our part. And thus we groan again under the old bondage of the law. Such an attempt to piece out the work of Christ by our own merit, Paul saw clearly, is the very essence of unbelief; Christ will do everything or nothing, and the only hope is to throw ourselves unreservedly on His mercy and trust Him for all.
J. Gresham Machen, Christianity and Liberalism