Kierkegaard poses this question. For him, it appeared that Protestantism needs Catholicism as its presupposition. The latter provided the law and guilt and penance necessary for sola fide to be a powerful witness to God’s grace. Without this Catholic backdrop, Protestantism lapses into a bourgeois sentimentality and liberal optimism. As a result, Luther’s stand against Rome makes little sense, except as an expression of the individual’s “free spirit” and other profound misunderstandings common in later Protestant triumphalism. In other words, the principles of the Reformation are secularized. Here is how Kierkegaard explains the matter:
Are not Catholicism and Protestantism related to each other like — it may seem extraordinary but is really so physically — like a building which cannot stand, to a buttress which cannot stand alone, whereas the whole is even very firm and secure, so long as they keep together, the building and the buttress which supports it. In other words: surely Protestantism, Lutheranism is really a corrective; and the result of having made Protestantism into the regulative has been to produce great confusion.
As long as Luther lived it could not be seen clearly, for he was continuously in the tense atmosphere of battle, and straining every nerve as polemicist, as well as in the smoke and steam of the battle, and as long as the fight continues there is something which corresponds to steam and smoke and which prevents one having either the time, the peace, or the clarity to see whether the point can be carried and the transposition made. Luther fought, it is always said, polemically against Catholicism: but it cannot be achieved in this way; it becomes clear how it ought to be done, but there is no time to stop, we must go on to the next point; we are fighting: but it cannot be achieved in this way, etc., and that is as far as it gets.
Then comes peace. Now we shall see whether Protestantism can stand by itself. Whether or not cannot perhaps be seen distinctly in a country where Catholicism exists side by side with Protestantism, for although they do not fight and each look to their own affairs there will be a reciprocal relationship at many points. In order to be able to see clearly whether and to what extent Protestantism can stand alone it is desirable to have a country where there is no Catholicism. There one would see whether Protestantism would not — presuming that it degenerated — lead to a form of corruption to which Catholicism — presuming it degenerated — did not lead, and whether that does not show that Protestantism is not fit to stand alone.
Let us try and realize this more clearly. It was after a heavy yoke had been upon men’s shoulders for a long, long time, after they had been frightened with death, judgement, and hell for generation to generation, with fasting and scourging, it was then that the bow broke. Out of a monastery cell broke the man Luther. Now let us be careful not to separate what belongs together, the background and the foreground, not to get a landscape without background, not to get something quite meaningless.
Now what Luther dared to do was, under the circumstances, the truth; for the opposite had been falsely exaggerated.
Luther then, broke out of the monastery. But that was not really the best opportunity of seeing with sweet reasonableness how much truth there was in the opposite, when it was not exaggerated. Luther knew he was hardly safe, and it was therefore rather a question of making use of the advantage he had won, by having broken out, in order to wound the opposite as deeply as possible.
Now take the order of things, just as they were when Luther broke out: they were in error: take away the assumption necessary for Luther, and Lutheranism is perfectly meaningless. Try and imagine that what Luther in extreme tension attacked as being the extreme, that it had become a sort of Result, in such a way that the extreme tension was omitted: and Lutheranism is absolute nonsense. Imagine a country, cut off from Catholic influence, to which this Lutheran Result had been brought — there the generation now living has never heard a single word about the aspect of the question which is expressed by the monastery, asceticism, etc., and which the Middle Ages exaggerated; on the contrary, it is brought up from childhood, softened from childhood with the Lutheran notion of calming an anxious conscience — thought it is important to note that there is not a soul who has made his conscience anxious, however distantly. What then is Lutheranism? Is there any sense in calming the anxious conscience, when the assumption: “anxious conscience” simply does not exist? Does not Lutheranism become meaningless, and what is worse, does it not become refinement, which will denote the difference between degenerated Protestantism and the corruption of degenerated Catholicism.
And that is exactly what I wanted to show, together with the fact that it indicates that Protestantism is not fit to stand alone.
After Kierkegaard further elaborates the “shallow worldliness” and “refinement” in mainline Protestantism, he closes with the following:
Luther set up the highest spiritual principle: pure inwardness. It may become so dangerous that we can sink to the lowest of lowest paganism (however, the highest and the lowest are like one another) where sensual debauchery is celebrated as divine worship; and so in Protestantism a point may be reached at which worldliness is honoured and highly valued as — piety. And this — as I maintain — cannot happen in Catholicism.
By why can it not happen in Catholicism? Because Catholicism has the universal premise that we men are pretty well rascals. And why can it happen in Protestantism? Because the Protestant principle is related to a particular premise: a man who sits in the anguish of death, in fear and trembling and much tribulation — and of those there are not many in any one generation.
[The Living Thoughts of Kierkegaard, ed. W. H. Auden, Indiana University Press, 1952, pp. 213-216, 219.]
Of course, Kierkegaard is assuming a basically Lutheran understanding of the law as primarily negative (condemnation), which is then overcome by the grace of God in the gospel (justification). As he sees it, the grace principle has eliminated the law principle in Protestant (Lutheran) countries, thereby both secularizing and paganizing the former. The Reformed (Calvinists) would ostensibly have a different understanding of law, as primarily an expression of grace, but it appears that Kierkegaard’s diagnosis would remain the same. De jure, grace fulfills the law; de facto, grace negates the law. When the law is forgotten, grace — as the awesome and wonderful and liberating power of God’s love — is also forgotten. Grace becomes an immanent property of culture and human identity, and when that happens it is game over for Protestantism.