Machen on the pure doctrine of the cross

"The lofty doctrine of divine grace, the centre and core of the gospel that Paul preached, did not always dominate the mind and heart of the subsequent church. The Christianity of the Apostolic Fathers, of the Apologists, of Irenaeus, is very different from the Christianity of Paul. 

The church meant to be faithful to the apostle; but the pure doctrine of the cross runs counter to the natural man, and not always, even in the church, was it fully understood. Read the Epistle to the Romans first, and then read Irenaeus, and you are conscious of a mighty decline. No longer does the gospel stand out sharp and clear; there is a large admixture of human error; and it might seem as though Christian freedom, after all, was to be entangled in the meshes of a new law" (J. Gresham Machen, God Transcendent, p. 129).

Marc D. Carpenter correctly responds to this Machen observation thusly:

“The pure doctrine of the cross runs counter to the natural (i.e., unregenerate) man.”  So true.  Why, then, was “the Christianity of the Apostolic Fathers, of the Apologists, of Irenaeus … very different from the Christianity of Paul”?  Why were/are professing churches not faithful to the doctrine the apostle Paul preached?  Come on, Machen, the logic is right there in front of your face.  It is because the Apostolic Fathers, the Apologists, Irenaeus, and all those in churches that are not faithful to the doctrine the apostle Paul preached, are/were NATURAL (i.e., unregenerate) MEN!  “The pure doctrine of the cross runs counter to the natural man.”  Does it run counter to the new creature in Christ, the one who has come from darkness to light, from blindness to sight?  Of course not.  So whenever you find a person who does not believe the pure doctrine of the cross (whether it is Joe Shmoe from Idaho or the “Apostolic Fathers”), you find the NATURAL MAN.  So simple, isn’t it?