Johannes Hohlenberg was born in Copenhagen in 1888. He wrote a biography about Soren Kierkegaard in Danish and it was translated into English in 1954.

Later Jean-Paul Sartre wrote about Kierkegaard, first in French in 1946, and then he was translated into English in 1960. And so began existentialism.

The first statement of the existential theme was made when the great age of German philosophy had culminated in the Hegelian system of dialectic. That imposing edifice of thought, which was to dominate the minds and disorder the affairs of generations to come, provoked a solitary Danish philosopher, Soren Kierkegaard, to vivid and voluminous contradiction. This remarkable man, to whom all existential thinkers acknowledge their indebtedness, led a life that was almost as uneventful externally as that of Oblomov, with an inward history that was even richer in emotional drama, and of a phenomenal intellectual activity. Never did a more troubled soul, or a more lucid and swift intelligence, seek enlightenment from the learned only to reject it as valueless. The case that he was continually arguing against the systematizers, original as it was in presentation, sparkling with humor, illustration and anecdote, was not so new as it was profound. He saw that most philosophy is not even wisdom after the event, but only wisdom about wisdom and little to do with any event. …. The literary works of this great writer are more theological than philosophical in the usually accepted sense of the word, but Kierkegaard’s talent for metaphysical discussion is undeniable. …. Distrusting all mysticism as much as he dislikes abstract philosophic theorizing, Kierkegaard bases his position upon individual man here and now, man in his passion and anxiety; and much of his argument is founded openly upon personal experience, including that of the erotic crisis of his life which was, externally, of an ordinary, almost commonplace description. He writes of man as a being with a passion for happiness – for an eternal happiness – and if this would not actually have been his definition of man, it is the only kind of man Kierkegaard writes for, or expects to understand him.

Introduction to Jean-Paul Sartre’s Existentialism and Humanism 1946 translated and introduced by Philip Mairet 1960

Existentialism and Humanism by Jean Paul Sartre

When man commits himself to anything, fully realizing that he is not only choosing what he will be, but is thereby at the same time a legislator for the whole of mankind – in such a moment a man cannot escape from the sense of complete and profound responsibility. …. This is the anguish that Kierkegaard calls “the anguish of Abraham.” You know the story: An angel commanded Abraham to sacrifice his son: and obedience was obligatory, if it really was an angel who had appeared and said, “Thou, Abraham, shall sacrifice thy son.” But anyone in such a case would wonder, first, whether it was indeed an angel and secondly, whether I really am Abraham. Where are the proofs? …. Who, then, can prove that I am the proper person to impose, by my own choice, my conception of man upon mankind? I shall never find any proof whatever; there will be no sign to convince me of it. If a voice speaks to me, it is still I who must decide where the voice is or is not that of an angel. If I regard a certain course of action as good, is it only I who choose to say that it is good and not bad. p. 30-31

Kierkegaard took up Sartre’s theme back in 1843 with his book Fear and Trembling. Abraham was righteous because he believed God. Kierkegaard called him the knight of faith and stressed his individuality. Abraham had an absolute relation to God, the Absolute. He couldn’t relate to the universal law about loving your son because of that relationship and he couldn’t explain himself to anyone.

“The paradox of faith is this, that the individual is higher than the universal, that the individual (to recall a dogmatic distinction now rather seldom heard) determines his relation to the universal by his relation to the absolute, not his relation to the absolute by his relation to the universal. The paradox can also be expressed by saying that there is an absolute duty toward God; for in this relationship of duty the individual as an individual stands related absolutely to the absolute.”

“So when in this connection it is said that it is a duty to love God, something different is said from that in the foregoing; for if this duty is absolute, the ethical is reduced to a position of relativity. From this, however, it does not follow that the ethical is to be abolished, but it acquires an entirely different expression, the paradoxical expression — that, for example, love to God may cause the knight of faith to give his love to his neighbor the opposite expression to that which, ethically speaking, is required by duty.”

“In the story of Abraham we find such a paradox. His relation to Isaac, ethically expressed, is this, that the father should love the son. This ethical relation is reduced to a relative position in contrast with the absolute relation to God. To the question, “Why?” Abraham has no answer except that it is a trial, a temptation (Fristelse) –terms which, as was remarked above, express the unity of the two points of view: that it is for God’s sake and for his own sake. In common usage these two ways of regarding the matter are mutually exclusive. Thus when we see a man do something which does not comport with the universal, we say that he scarcely can be doing it for God’s sake, and by that we imply that he does it for his own sake. The paradox of faith has lost the intermediate term, i.e. the universal. On the one side it has the expression for the extremest egoism (doing the dreadful thing it does for one’s own sake); on the other side the expression for the most absolute self-sacrifice (doing it for God’s sake). Faith is this paradox, and the individual absolutely cannot make himself intelligible to anybody.”

“Even If a man were cowardly and paltry enough to wish to become a knight of faith on the responsibility and at the peril of an outsider, he will never become one; for only the individual becomes a knight of faith as the particular individual, and this is the greatness of this knighthood, as I can well understand without entering the order; but this is also its terror, as I can comprehend even better.”

From Chapter 4 of Fear and Trembling Problem Two: Is There Such a Thing as an Absolute Duty Toward God?

Robert Perkins edited many commentaries on Kierkegaard’s books. He also wrote a biography about Kierkegaard in 1969. Read it here.