Kierkegaard wrote Either/Or soon after receiving his doctorate and breaking his engagement with Regine Olsen. Either/Or is his first major work and remains one of his most widely read. Kierkegaard wrote the book under a series of false names, or pseudonyms. The book has two parts: the first deals with the aesthetic, a word that Kierkegaard uses to denote personal, sensory experiences. The second part of Either/Or deals with ethics. In this part Kierkegaard discusses the merits of a social and morally proper life. Kierkegaard wrote the first section under the simple pseudonym “A,” although he wrote the last section of part I, “The Diary of the Seducer,” under the pseudonym “Johannes Climacus.” Kierkegaard wrote part II under the interchangeable pseudonyms “B” and “the Judge.” We know now that Kierkegaard himself wrote the entire book, but when Either/Or was first published few people knew the author’s actual identity. A claims that the aesthetic finds its highest expression in music, the theatre, and love. However, the source of love and the arts’ aesthetic power lies in their ability to inspire the imagination. A considers the imagination to be the most useful tool in obtaining aesthetic pleasure. B argues that living an ethical life is preferable to the aesthetic life.

Music and drama create different kinds of aesthetic experiences. The aesthetic pleasure offered by music is the most direct. The very best music affects the imagination immediately. The pleasures to be found in drama—which is too concrete and intellectual to directly fire the imagination—lie in the viewer’s opportunity to pretend to be someone else. The pairing of music and drama can be a particularly transcendent aesthetic experience. A praises Mozart’s Don Giovanni, an opera based on the story of the great lover Don Juan. The music in Don Giovanni can be enjoyed on its own, and it is equally enjoyable to pretend to be Don Juan. However, the opera teaches a valuable aesthetic lesson as well, because Don Juan is the ultimate selfish aesthete. Repetition dulls the pleasure of an act, so Don Juan never repeats the act of love more than once with the same woman. Although he never sleeps with the same woman twice, by so doing he continually repeats the act of sleeping with a new woman. He can never enjoy the woman he is with because he is in such a hurry to get to the next one. A is devoted to pleasure as well and sees repetition as an enemy of pleasure. However, A believes that obtaining true aesthetic pleasure requires a more measured approach than blindly following one’s passions, as Don Juan does.

The extreme difficulty of achieving true aesthetic pleasure leads A to claim that boredom is the most common, and unpleasant, human state. In fact, A goes so far as to claim that it is the root of all evil and makes a number of proposals for how it ought to be dealt with. One such plan is for Denmark to borrow a large sum of money and devote it explicitly to the entertainment of the masses. There are also more personal measures one can take to avoid boredom. A suggests that when receiving mail, one ought to leave it unopened for three days because the pleasure of imagining what is in the envelope far exceeds the pleasure to be gained from actually reading the letter.

Johannes Climacus, the pseudonymous author of the “The Seducer’s Diary,” which is the most famous section of Either/Or, further explores how to maximize aesthetic pleasure. “The Seducer’s Diary” is Johannes Climacus’s detailed, firsthand account of his wooing a young woman named Cordelia. For the majority of the diary, Johannes Climacus plots the seduction very slowly and deliberately. He takes great pleasure out of planning the seduction and doesn’t even speak to Cordelia until the last quarter of the diary. Once Johannes Climacus makes his move, things happen very quickly, and he’s soon engaged to Cordelia. He isn’t satisfied with the success of his seduction, however, until he has deliberately driven Cordelia to break the engagement and then, later, to come back to him. At this point he is finished with her and goes to find a new woman to seduce. Once Johannes Climacus has exhausted all the imaginative and exciting possibilities with Cordelia, continuing his relationship with her would lead him to boredom.

The second part of Either/Or, written under the pseudonyms B and the Judge—who eventually converge into a single character—takes the form of a letter written by the Judge to A. The letter is a response to part I of Either/Or; in it, the Judge attempts to persuade A that the ethical life is better than the purely aesthetic life. First, the Judge attempts to defend marriage. The Judge claims that the ethical life of being married is better than the aesthetic life of the seducer, and the Judge makes this claim on an aesthetic basis. The Judge says that there is actually more aesthetic pleasure to be found in a consistent marriage than in a bachelor life. The judge draws a distinction between the ethical, forward-looking repetition of the married life and the aesthetic, backward-looking recollection of the confirmed bachelor. He further points out that romantic literature always focuses on what happens before marriage but not what happens after, and he claims that the aesthetic fear of repetition is actually cowardly and selfish. The Judge argues that romantic love can exist in marriage and goes so far as to say that marriage is the highest form of romantic love. The ethical courage to submit to repetition is rewarded by the consistent, reliable aesthetic pleasure found in a loving marriage.

The Judge goes on to claim that A’s devotion to the aesthetic prevents A from making any significant choices. Although A has a far wider range of options than the Judge, the Judge argues that since the Judge’s choices are limited by ethics—by a consideration of other people—his choices are much weightier and mean much more to him than A’s aesthetic choices mean to A. The aesthetic has its place, the Judge agrees, but the place of the aesthetic is beneath the ethical. The Judge’s actual loving relationship with his wife is far better, the Judge argues, than the largely imaginary relationship between Johannes Climacus and Cordelia. The Judge experiences his pleasure with another person, while a seducer’s pleasure is completely in his or her imagination. Part II ends with a sermon that the Judge has received from a friend. The sermon is entitled “The Edification Which Lies in the Fact that in Relation to God we Are Always in the Wrong.” The sermon’s key point is that humans, whether their choices are aesthetically or ethically motivated, are never in the right. Only by accepting that God is always right, and by trying to do God’s will, can a person escape unhappiness.