As surprising as it may seem to some, the church grows and matures in her understanding over time. In other words, some battles are actually won, and certain doctrines are really established, and they stay established. Some of this can be seen in the pages of the New Testament, and other examples are found at subsequent periods in the history of the Church. After the decisive battle has been fought and won, some may seek to question the victory – but the victory remains firmly in place. Today, if some diehard Bonapartist tried to question the effect of Waterloo on his cause, though he has a right to his opinions, the history of the thing is settled. If an even more persistent follower of Marc Anthony wanted to refight the battle of Actium, we would probably have grounds to question his emotional stability.
It is the same in the realm of the Church’s creedal understanding. Interestingly, God has used certain key individuals to fight to establish certain truths, and as a result today those truths are set in concrete, despite what the occasional stray heretic may want to say. The dogs can bark, but the train keeps going.
The sovereign God consistently uses earthen vessels to display His glory. Athanasius was used to place the doctrine of Christ’s full Deity beyond question in the Christian church. Augustine was used in a similar way on the question of man’s sinfulness. Martin Luther pointed to the article of a standing or falling faith, the doctrine of justification by faith alone. And Anselm is the one we may thank for our understanding of the substitutionary nature of the atonement.
Of course, these post-apostolic men did not invent these doctrines, or even state them in perfect purity. The doctrines had already been taught in the Bible, and the men used by God to give us the Bible knew, understood, and instructed the first Christians in these things. But nothing tests fidelity like the temptation to fall. When these scriptural doctrines were assaulted, the men used in these situations moved the Church out of her probationary period on that particular issue. God brings heretics to test us, to see if we really love Him as we claim, and, as church history demonstrates, He does this in various areas. "Thou shalt not hearken unto the words of that prophet, or that dreamer of dreams: for the LORD your God proveth you, to know whether ye love the LORD your God with all your heart and with all your soul" (Dt. 13:3). When a false teacher like Arius arises and attacks the Deity of Christ, the Lord is seeing if the Church really loves Him enough to defend His honor. When a false teacher like Pelagius seeks to flatter us by telling that we are not native-born sinners, the Lord is seeing if the Church will remain true to Him. Do we stand with the Word, which tells us the harsh truth about ourselves, or do we go with the one who airbrushes out all our flaws?
All doctrines have to be taught, including those described here. But many doctrines no longer have to be "worked through." The Church must faithfully teach the doctrine of the Trinity, but we do not have to work through it as was done in the run-up to Nicea. But apart from the fact of the Second Coming, the universal Church still has to work through the doctrines related to eschatology. In the same way, the doctrine of the substitutionary death of Christ has been settled, no small thanks to Anselm.
So this is the process. But one of the dangers that comes with great victories is the sin of ingratitude. Every day we enjoy countless blessings which are the result of battles fought before we were born. This is of course true on a physical level, as we recognize whenever we seek to remember those who have fought and died for our civic freedoms. But the same thing is true in the history of the Church, and it is perilously easy to take our wonderful heritage for granted. We do not really have an ecclesiastical "Memorial Day."
This problem can be seen in fundamentalist churches which strongly emphasize the substitutionary death of Jesus Christ. But our dear brothers on the ecclesiastical right-wing would also rather be dead in a ditch than to acknowledge that they are indebted to St. Anselm of Canterbury for their understanding. This is not the purity of separatism, but rather the sin of ingratitude.
This whole issue is problematic for modern Protestants because we like to pretend that we do not need to have a doctrine of tradition, of creedal advance. But classical, historic Protestantism had such an understanding -- which they were able to sharply distinguish from the Roman Catholic excesses concerning tradition. But we, in the grip of modernity, fear that any appreciation of our doctrinal history, of our tradition, puts us squarely "on the road to Rome."
What it actually does is reaffirm our faith in the sovereignty of God, who preserves His Church, even through great corruptions, and who brings even greater reformations. And in these reformations, He never starts "from scratch." He keeps, and allows us to pass on, those things which He has bequeathed to the Church. The heritage we have is not one that arose from perfection, but it is most certainly precious.