The possibility of freedom is not that we can choose between good and evil. Such nonsense is no more compatible with Scripture than with thinking. Possibility—is that we can.
It has become clear to us now, I think, what Luther had in mind when he spoke of the bellua qua non occisa homo non potest vivere. In these words, as if in embryo, is contained all of existential philosophy as distinct from theoretical philosophy: its ultima ratio is not "laws," which deny man protection, but homo non potest vivere, and conflict is its method of seeking the truth. Now we will also be able to understand Luther's violent hatred of human wisdom and human knowledge, a hatred which was nurtured and sustained in him by the Apostle Paul's teaching about love and grace. I shall cite two passages from Luther's commentary on the Epistle to the Galatians; they will enable us to come closer still to the sources of Kierkegaard's existential philosophy, and to see for ourselves the abyss which separates it from the existential philosophy of the Greeks. Luther writes: Ergo omnia dona quae habes, spiritualia et corporalia, qualia sunt sapientia, justitia, eloquentia, potentia, pulchritudo, divitiae, instrumenta et arma sunt ipsius tyrannidis infernalis (h. e. peccati), hisque omnibus cogeris servire diabolo, regnum ejus commovere et augere ("All the gifts you enjoy—wisdom, righteousness, eloquence, strength, beauty, wealth—all these are the tools and weapons of the infernal tyrant (i.e., sin) and they all compel you to serve the devil, to secure and increase his kingdom").
And in another passage, with even greater force and emphasis: Nihil fortius adversatur fidei quam lex et ratio, neque illa duo sine magno conatu et labore superari possunt, quae tamen superanda sunt, si modo salvari velis. Ideo, cum conscientia perterrefit lege et luctatur cum judicio Dei, nec rationem, nec legem consulas, sed sola gratia ac verbo consolationis nitaris. Ibi omnino sic te geras, quasi nunquam de lege Dei quidquam audieris, sed ascendas in tenebras, ubi nec lex, nec ratio lucet, sed solum aenigma fidei, quae certo statuat te salvari extra et ultra legem, in Christo. Ita extra et supra lucem legis et rationis ducit nos evangelium in tenebras fidei, ubi lex et ratio nihil habent negotii. Est lex audienda, sed suo loco et tempore. Moses in monte existens, ubi facie ad faciem cum Deo loquitur, non condit, non administrat legem, descendens vero de monte legislator est et populum lege gubernat (Ibid., 169: "Nothing conflicts with faith more than law and reason, and it is impossible to overcome them without immense effort and labor—but nevertheless they must be overcome if you wish to be saved. Therefore, when your conscience, terrified by law, struggles against the judgment of God, do not consult reason or law, but rely wholly upon the grace and Word of divine consolation. Hold fast to this, as though you had never heard of law, and enter the darkness where neither law nor reason lights your way, but only the mystery of faith, which gives you assurance that you will be saved apart from and beyond the law, in Christ. Thus, the Gospel leads us beyond—and above—the light of law, into the darkness of faith, where there is no room for reason or law. Law must be heard—but at its own time and in its own place. When Moses was on the mountain, where he spoke face to face with God, he knew no law, and did not rule by law; when he descended from the mountain, he became a lawgiver, and ruled his people through law").
I have already mentioned that Kierkegaard had read little of Luther. But Luther's sola fide, which inspired his commentary on Galatians, as well as his other writings, completely dominated Kierkegaard's thinking. As long as philosophy has its source in wonder, it finds its fulfillment in "understanding." But what can "understanding" offer man when philosophy is approached by despair, with its questions made from lugere et detestari? All the "gifts" of which reason customarily boasts—wisdom, righteousness, eloquence-are helpless against despair, which signifies in itself the end of all possibilities, the ultimate inevitability. What is more, these gifts are found to be, not allies, but merciless enemies—the servants of "a tyrant that compels man to serve the devil." The truths of reason—and the laws ordained by it—which are, at their own time and in their own place, both useful and necessary, cease to be truths when they become autonomous, liberated from God (veritates emancipatae a Deo), when they clothe themselves in the vestments of eternity and changelessness. Having become petrified themselves, they turn to stone all those who look upon them. The ordinary consciousness thinks this is madness.
Perhaps it is madness: how could anyone exchange light for darkness? Not only to Bonaventura, but to all of us, it seems self-evident, and absolutely indisputable in its self-evidence, that faith is upheld by truths; that, consequently, faith can be defended by the same means which serve to attack it; and that, if we deny this, we discredit faith forever. But the Scriptures revealed something entirely different to Luther: when Moses stood face to face with God, all truths, all laws vanished in an instant, evaporated as if they had never been. Moses was defenseless. And only then did he become a prophet and share the power of God. All the fears, all the apprehensions which force man to seek support, protection, assistance were suddenly dispelled as if by the wave of a magic wand. The light of reason grew dim, the bonds of law were loosed, and in this primeval "darkness," this limitless freedom, man once again found himself in contact with the fundamental valde bonum ("very good") which filled the world before our forefather's disastrous Fall. And only in this "darkness of faith" does man's original freedom return to him: not the freedom which Socrates knew and described to men, freedom of choice between good and evil, but the freedom which, to use Kierkegaard's words, is possibility. For if man must choose between good and evil, this means that freedom has already been lost; evil has entered the world and become the equal of God's valde bonum.
Man has, must have, an immeasurably greater and qualitatively different freedom: not the freedom of choosing between good and evil, but that of ridding the world of evil. Man cannot have any sort of dealings with evil; as long as evil exists, there is no freedom, and all that man has called freedom so far is an illusion, a fraud. Freedom is not the choice between good and evil; it destroys evil, turns it into Nothingness—and not the menacing Nothingness of which we have been speaking until now, a Nothingness which in some strange way assumed immense power to ruin, destroy, annihilate everything in its path, and thus took its place beside, and even above, the Existing and gained exclusive control over the predicate of Being—but Nothingness as it was when, weak and powerless, it was transformed according to the word of the Creator into valde bonum. As long as Nothingness has not been decisively destroyed, man cannot even dream of freedom. On the contrary, true freedom, which was lost to us at the moment when our forefather, under an incomprehensible and mysterious spell, turned from the tree of life and tasted the fruit of the tree of knowledge, will return only when knowledge loses its power over man, when he finally sees that the "eager striving of reason for general and necessary truths," i.e., for veritates emancipatae a Deo, is the concupiscentia invincibilis (unconquerable craving) through which sin came into the world. We will recall that even Kierkegaard thought that ignorance is the sleep of the mind. In the midst of many other eternal truths, this one appears to us to be the unshakable and self-evident truth par excellence. However, it is not a truth, but a delusion, the deepest of sleeps, very nearly the death of the mind. Knowledge enslaves human will, making it subordinate to eternal truths which by their very nature are hostile to everything that lives and is at all capable of demonstrating its independence, and which cannot bear to have even God as their equal.
The "swoon of freedom"  which Kierkegaard connects with the Fall of man is also the prerequisite for the possibility of the existence of knowledge, which The Critique of Pure Reason actually could not, and would not, take into consideration. And, conversely, the state of ignorance, the state of freedom from knowledge is the source of man's liberation. Ignorance is not something negative, some sort of lack, some sort of deficiency, just as freedom is not insufficiency and negation, but an affirmation of great worth. Innocence has no desire for knowledge; it is above knowledge (let me remind you once more of the words of Plotinus: drameîn hyper tên epistêmên), just as the will of the One Who created man in His own image and likeness is above knowledge. Kierkegaard himself gives us the best evidence of this. "Fear is the swoon of freedom," he tells us. "Psychologically speaking, the Fall always takes place in a swoon." And he goes on to explain: "The Nothingness of fear is a complex of misgivings to which the individual comes ever nearer, even though they have essentially no significance in the fear; however, this is not a Nothingness to which the individual has no relationship, but a Nothingness which has a vital mutual relationship with the ignorance of innocence." The first step of knowledge is this:
Nothingness, which is supposed to be Nothingness, and which is only Nothingness, breaks its way into the soul of man and begins to take charge there, as if it were in fact the master. Kierkegaard has confirmed this for us: crede experto—which means, do not ask the old, ask the experienced. His testimony has such great significance that I feel obliged to reproduce it again in full, as it is only by going through the experience of Kierkegaard and of minds akin to his that one can become at all free of the fatal temptation which attracts us to the tree of knowledge, and begin to ponder seriously the story of Genesis. "If we ask what the object of fear is, there will be only one answer: Nothingness. Nothingness and fear accompany each other. But as soon as the real freedom of the mind is disclosed, fear disappears. What, upon closer scrutiny, is Nothingness as the pagans feared it? It is called fate... Fate is the Nothingness of fear... The greatest genius has no power to vanquish the idea of fate. On the contrary, the genius reveals fate everywhere, understanding it all the more profoundly, as he himself is more profound... This precisely describes the real power of the genius, that he reveals fate, but this is also his weakness. This seems nonsense to the ordinary consciousness—but in fact something great is concealed here, for no man is born with the idea of providence... The existence of such genius is, in spite of its brilliance, its beauty, and its great historical significance, a sin. It takes courage to understand this, but it is so." [V, 93, 96, 99]
There is no doubt that it takes courage—great courage, immense courage—to understand this and to dare to say such a thing aloud. For then it must be admitted that in ignorance the mind is wide-awake and that knowledge induces lethargy and sleep in man. The Biblical narrative must not be "amended"; the Fall was the beginning of knowledge, or, to be more exact, sin and knowledge are only different words to denote one and the same "subject"! The man who knows, the man who is not satisfied with experience, the man "who is irritated by experience" and who "eagerly strives to assure himself that what is must necessarily be thus (as it is), and not otherwise"—reveals a Fate which does not exist.  For man in the state of ignorance, Fate does not exist, and Fate has no way to make him yield as long as he continues in ignorance. But then a new light dawns for us in the person of the serpent, whom we "knowing" men regard as an irrelevant appendage to the Biblical story. The renunciation of the "ignorance of innocence" is a great enigma. Of what use was knowledge to the first man when he was entrusted with the power to give names to all things? Of what use was it for him to exchange the divine valde bonum, in which there was no room for evil, for a world in which both good and evil exist, and where one must be able to tell good from evil? We have no doubt that the ability to distinguish between good and evil improves man and represents the progress and growth of his mind. Even Kierkegaard, in paying tribute to this human, all too human, notion of good and evil, shifts back and forth from Socrates to the Bible and from the Bible to Socrates, and feels obliged to admit that the first man, before the Fall, i.e., before he tasted the fruit of the forbidden tree, was somehow not quite complete, not a real man, precisely because he did not know how to distinguish good from evil. One might almost say that the sleep of the mind, which was, according to Kierkegaard, the state of existence of the first man, really means that he was not yet able to distinguish between good and evil. And so it turns out that the serpent did not deceive man—the Fall was by no means a Fall, but only a necessary moment in the dialectical development of the spirit, as Hegel has told us. Of course, Kierkegaard does not mean this—and yet, when he denies the presence of freedom in man in the state of innocence, he automatically connects this with his inability to distinguish good from evil. And this is the same Kierkegaard who so passionately assured us that freedom is not the possibility of choosing between good and evil, that such an interpretation of freedom is nonsense, that freedom is possibility. 
And, in fact, this is the problem: if freedom were the freedom of choice between good and evil, then this freedom would have to be inherent in the Creator Himself, as the free Being par excellence. And, therefore, it would be quite possible to assume that, having a choice between good and evil, the Creator would prefer evil. This question was the real crux interpretuum for medieval philosophic thought. It was impossible to reject the idea that freedom is the freedom of choice between good and evil: the Middle Ages, limited by Hellenic speculation, could not, dared not, separate the religious point of view from the ethical. Neither was it possible to think that God has a "right" to prefer evil over good.
From this "irreconcilable contradiction"—which symbolized the age-old opposition between Biblical revelation and speculative philosophy—arose the "paradoxical" teaching of Duns Scotus, who overturned all the traditional principles upon which his predecessors had constructed the Christian ethic. He was the first who ventured to utter those terrible words which the rational understanding cannot endure and which even devout philosophers have been careful to avoid: free will. God is free will; there is no principle above God, no law. Whatever He accepts is good. Whatever He rejects is evil. God does not, as Plato thought, choose between good and evil, bestowing His love upon good and hating evil; on the contrary: what He loves is good and what He does not love is evil. God created both good and evil out of Nothingness, which offered Him no resistance, just as He made the whole world out of nothing. The Scholastic philosopher William of Ockham, who followed Duns Scotus, developed the same thesis with even greater clarity. There can be no question that the theories of Duns Scotus and Ockham are in complete accord with both the spirit and the letter of Holy Scripture. But to speculative philosophy, free will and totally unlimited freedom, even though they are God's, sound like a sentence of death.
Speculative philosophy cannot construct anything upon "free will"; it loses its footing. And, indeed, Ockham and Duns Scotus are the last independent thinkers of the Middle Ages; after them the "decline of Scholasticism" begins, just as a further development of Hellenic philosophy was impossible after Plotinus and his drameîn hyper tên epistêmên. It is necessary either to "soar" above knowledge, "soar" above the ethical, or, if such soaring is not within a man's power, or is actually impossible for him, to renounce "revelation" forever, renounce Him Who appears in revelation, and humbly take up the burden of eternal truths and uncreated laws. Modern philosophy has chosen the second path—where it leads will be shown presently—but the Middle Ages dreaded eternal truths and uncreated laws no less than divine free will. They guessed almost intuitively that truth and law, like man, do not gain their meaning, significance, and worth from their uncreatedness and their independence from God; that uncreatedness and independence from God not only do not add anything of value to them, but take away their very essence. All that is uncreated is also lacking in grace, disadvantaged, and, accordingly, condemned to an illusory existence. All that is "liberated" from God surrenders itself to the power of Nothingness. "Dependence" upon God is freedom from Nothingness, which, because it is uncreated, sucks the blood from everything living, like a vampire. Kierkegaard's account of how Inflexibility had paralyzed not only him, a weak human being, but even the Creator Himself, shows us quite vividly what truth and principles become when they forget their subsidiary function and try to assume sovereign rights. However, in the interests of both historical truth and the problems which occupy us here, I must say that the Middle Ages were not as monolithic in their formulation and resolution of basic religious questions as some would like us to think, and they were not always so subordinate to Greek influence.
In its principal course, medieval philosophy, which was very closely linked with patristic philosophy, on the whole simply kept to the legacy of Hellenism, and, even in the person of its most outstanding representatives, dared not and would not break with Hellenism. It is possible and usual, without offending reality, to describe its broad mainstream as leading from Origen and Clement of Alexandria, on the one hand, and St. Augustine, on the other, down to the beginning of the fourteenth century. But in the middle of that century another current appeared, faint and far away, to be sure, which reflected an awareness of the impossibility and uselessness of reconciling Biblical revelation with the rational truths of Greek philosophy. Even Tertullian, whom we rightly consider to be, to a certain degree, Kierkegaard's inspiration and his spiritual father—we have already mentioned this, and will now do so again—even Tertullian realized what a fathomless abyss separates Jerusalem and Athens. However, a particularly brilliant example of this trend was Peter Damian, who in his writings (especially in the book De omnipotentia Dei) rebelled, almost four centuries before Duns Scotus and Ockham, with a boldness that amazes us even now, against attempts to interpret Holy Scripture with the help of and on the basis of Hellenic philosophy. He was horrified at the "Necessity" of acknowledging any kind of limit to the omnipotence of God. In the presence of God every Necessity reveals its true nature and is exposed as vain and empty Nothingness. Even the assumption that the law of contradiction or the principle: quod factum est infectum esse nequit ("what has once existed cannot become nonexistent") could in any sense bind God or oblige Him at all seemed to him to be a repudiation, a defiance of Holy Scripture and the greatest offense: cupiditas scientiae, which led man to the Fall. Qui vitiorum omnium catervas moliebatur inducere, cupiditatem scientiae quasi ducem exercitus posuit, sique peri eam infelici mundo cunctas iniquitatum turmas invexit ("He who introduced the swarm of vices placed at their head, like a leader of troops, the thirst for knowledge, and thus condemned the unhappy world to an immense number of misfortunes").
What Kant's "critique" regarded as the natural function of pure reason, what theologians have seen, and see to this day, as partem meliorem nostram—the thirst for knowledge, which tells us that what exists must necessarily exist thus (as it does exist) and not otherwise—was in the eyes of the medieval monk original sin, from which his entire soul shrank as from the corrupt breath of death and destruction. There is no principle, ideal or real, that could have existed before God, that could be above God. All power in the universe belongs to God; God always commands, never obeys. Every attempt to place anything whatever above God—regardless, I repeat, of whether it be ideal or material—leads to an "abomination of desolation." That is why Christ, when asked what the first commandment was, answered by repeating the thunderous audi Israel, which demolishes both the knowledge of pure reason and all the necessities on which the knowledge of pure reason is based. Tertullian, from whom Kierkegaard borrowed his idea of the Absurd, also took Scripture as a declaration that for God everything is possible. It is true that Tertullian did not say credo quia absurdum—words ascribed to him by Kierkegaard and most of his contemporaries. But in his De carne Christi we find the same idea even more defiantly expressed.
I have mentioned it before, but in view of the close connection between Kierkegaard's theory of the Absurd and Tertullian's approach to Biblical revelation, I feel that at this point I must once again quote these lines, which are unique even in theological literature: Crucifixus est Dei filius; non pudet, quia pudendum est. Et mortuus est Dei filius; prorsus credibile quia ineptum est. Et sepultus resurrexit; certum est, quia impossible ("The son of God was crucified; it is no cause for shame, because it is shameful. And the son of God died; it is credible, because it is absurd. And, having been buried, he rose again; it is certain, because it is impossible"). The meaning of the Biblical "Hear, O Israel" is revealed here with a sharpness and intensity that mortal men can hardly bear. Discard your notions of what is shameful, absurd, impossible; forget your eternal truths: they all come from the Evil One, from the fruit of the forbidden tree. The more you rely on your "knowledge" of good and evil, of rational and irrational, of possible and impossible, the further you will be from the source of life and the stronger will be the power of Nothingness over you. The greatest genius, the most virtuous man, is the most terrible sinner. Between Athens and Jerusalem there is no peace, nor should there be. Rational truth comes from Athens; revelation, from Jerusalem. There is no room for revelation within the limits of rational truths; it breaks through such limits. And revelation is not afraid of rational truths: to all their pudendum, ineptum et impossibile it replies with its authoritative non pudet, prorsus credibile and, crowning all, its certum; and the ordinary categories of thinking begin to seem like a dense fog enveloping Nothingness, which, though weak and helpless, appears to everyone to be menacing and invincible.
Neither Tertullian, nor Peter Damian, nor all the others who came with them and after them, were triumphant in history. —But I will ask again: is not the ultimate and most necessary truth to be found in the very voices that so infrequently reach our ears? And do not our pudet, ineptum, impossibile, which history takes such pains to defend, conceal the presence of that bellua, qua non occisa home non potest vivere?
Kierkegaard, in venturing to declare that for God everything is possible, departed from the broad road along which thinking humanity, even Christianly thinking humanity, is moving. For him, "triumphant," "victorious," recognized Christianity was a Christianity that had abolished Christ, i.e., God. But on paths unknown to anyone, in wildernesses where no one had even made paths, his ears caught the silent voices of men unknown and unnecessary to anyone: men with the "courage" to look at what madness and death reveal to us. They have seen and heard things that no one has ever heard and seen before. That is why they have nothing, not even language, in common with all the others; these are men who have "withdrawn from the general," as Kierkegaard puts it.  Everyone else "rejects" the miraculous, in order to contemplate and rejoice in pure charity, which can do nothing. In our world, where there are no miracles, charity and love are powerless and helpless, and, apart from "spiritual" satisfaction, they have nothing to offer man. In order to return to them the force and power they deserve, one must reject all the "consolations" of ethics, beneath which hide the "impossibilities" of reason, the captive of nonexistent Nothingness. It is difficult, immensely difficult, to renounce reason and the awareness of one's righteousness; for this means to "withdraw from the general." As long as a man goes along with everyone else, he has a sense of stability, of strength, of support—he has a "solid footing." He upholds the rest, but to an even greater extent all the rest uphold him; that is the ultimate and principal temptation of the rational and the ethical. This is why Plato could say that the greatest of all misfortunes is to become a misologos. It is a misfortune, and a terrible one. But surely it is an even greater misfortune to trust in reason and the ethical. They lead us to all-engulfing Nothingness, and Nothingness becomes lord of the universe. And there is no salvation from Nothingness; Nothingness is the very monster qua non occisa home non potest vivere. As long as a man relies upon the support of the "general," as long as he is afraid to lose his footing, as long as he puts his faith in the truths of reason and his own virtues, he is wholly in the power of his worst and most implacable enemy.
 "The swoon of freedom" is a free translation of Luther's "de servo arbitrio"—the enslaved will, i.e., the will which seeks truth, not through faith, but through reason.
 The words in quotation marks are taken, as the reader will probably recall, from The Critique of Pure Reason. —I have italicized only the words "must necessarily."
 V, 44. "The possibility of freedom is not that we can choose between good and evil. Such nonsense is no more compatible with Scripture than with thinking. Possibility is that we can."
 "The knight of faith knows how beautiful and joyous it is to belong to the general. He knows how soothing it is to be an individual who adapts himself to the general, and, so to speak, publishes a second edition of himself: neat, pleasing to the eye, without errors, easy for all to read; he knows how good it is to understand yourself in the general, so that you yourself understand the general, and every other person who understands you, understands you in the general, and together with you rejoices in the peace which the general offers the soul. He knows how beautiful it is to be born the sort of man who has the general as his fatherland, for whom the general is an unfailing haven where he will always be received with open arms, where there must be refuge for him. But he knows that a lonely road, narrow and steep, winds above the general; and he knows the horror of being born lonely, of being born outside the general, of being condemned to go through life without meeting a single traveler along the way. He sees very clearly what his relationship is to other people. Humanly speaking, he has gone mad, and cannot make anyone understand him. And yet, "gone mad" is the very mildest expression. If they do not take him to be mad, people will declare him a hypocrite, and the higher he goes on his path, the more he will seem to all an utter hypocrite." (III, 72, 73)
And again (ibid., p. 68): "Faith cannot be achieved by means of the general; that would mean abolishing it. Here lies the paradox of faith, and one man cannot understand another in this matter. We imagine that if two people are in the same position, they will understand one another... But one knight of faith can in no way help another knight of faith. A man can become a knight of faith only if he will wholeheartedly take upon himself the paradox—otherwise he will never become a knight of faith. Comradeship is unthinkable in this realm. Each man must decide for himself what he understands his own Isaac to be... And if anyone should prove to be cowardly and mean enough to wish to become a knight of faith by placing the responsibility for it upon another—it would not matter; nothing would come of it. For only an individual, just as an individual, can become a knight of faith. There is something great in this which I can understand, but not attain. There is also something terrible in it—which I understand even better."