False "Gospels" - Fesko on Machen

My question is: How many different ways... how many paths... how many spiritual exercises and legal obediences have been added to Christ's finished work throughout the ages that falsely point Christians in the supposed "sure" way of securing their salvation? In a word, one... that of works. John Fesko elaborates by unpacking J. Gresham Machen's thought on the matter:

 "Machen was aware of the different ways by which ancient and modern humanity proposed to extricate themselves from the pit of sin and death. Machen rejected mysticism as an approach to God and redemption because mystics believe that communion with God is based in “ineffable experience,” whereas the Bible teaches that a premium is placed upon understanding and knowing the truth...

"Certainly, then, a person must believe in God, but should he also not contribute to his salvation in some way? Machen identified this combination of faith and works as a false gospel. In his lecture notes on Galatians, Machen writes, “The enemy against which Paul is fighting in the Epistle can be reconstructed fairly well from the Epistle itself. Paul was fighting against the doctrine that a man can earn a part, at least, of his salvation by his own obedience to God’s law; he was fighting against the doctrine that a man is justified not by faith alone, but by faith and works.” Machen knew that Paul’s opponents, the Judaizers, though an ancient foe of the gospel, had descendants in his own day: So the error of the Judaizers is a very modern error indeed, as well as a very ancient error. It is found in the modern Church wherever men seek salvation by “surrender” instead of by faith, or by their own character instead of by the imputed righteousness of Christ, or by “making Christ master in the life” instead of by trusting in His redeeming blood. In particular, it is found wherever men say that “the real essentials” of Christianity are love, justice, mercy and other virtues, as contrasted with the great doctrines of God’s Word. These are all just different ways of exalting the merit of man over against the Cross of Christ; they are all of them attacks upon the very heart and core of the Christian religion. Machen rejected all other approaches to salvation —mysticism, pantheism, moralism, and legalism— and recognized that there was only one way to be saved—by faith alone, in the person and work of Christ alone, by God’s grace alone." 

-- John V. Fesko, Machen and The Gospel