During the following three years (1843-5) Kierkegaard, once roused to productivity, though undoubtedly kept at his task by the exertion of marvelous will-power, wrote in quick succession some of his most notable works--so original in form, in thought, in content that it is a well-nigh hopeless task to analyze them to any satisfaction. All we can do here is to note the development in them of the one grand theme which is fundamental to all his literary activity: how to become a Christian. If the second part of "Either-Or" was devoted to an explanation of the nature of the ethical, as against the æsthetic, conduct of life, inevitably the next task was, first, to define the nature of the religious life, as against the merely ethical life; then, to show how the religious sphere may be attained. This is done in the brilliant twin books _Frygt og Baeven_ "Fear and Trembling" and _Gjentagelsen_ "Repetition." Both were published over pseudonyms. "Fear and Trembling" bears as its subtitle "Dialectic Lyrics." Indeed, nowhere perhaps is Kierkegaard's strange union of dialectic subtlety and intense lyrical power and passion so strikingly in evidence as in this panegyric on Abraham, the father of faith. To Kierkegaard he is the shining exemplar of the religious life; and his greatest act of faith, his obedience to God's command to slay Isaac. Nothing can surpass the eloquence with which he depicts the agony of the father, his struggle between the ethical, or general, law which, saith "thou shalt no kill"! and God's specific command. In the end, Abraham by a grand resolve transgresses the law; and lo! because he has faith, against certainty, that he will keep Isaac, and does not merely resign him, as many a tragic hero would have done, he receives all again, in a new and higher sphere. In other words, Abraham chooses to be "the exception" and set aside the general law, as well as does the æsthetic individual; but, note well: "in fear and trembling," and at the express command of God! He is a "knight of faith." But because this direct relation to the divinity necessarily can be certain only to Abraham's self, his action is altogether incomprehensible to others. Reason recoils before the absolute paradox of the individual who chooses to rise superior to the general law.