Either/Or, published in 1843, presents contrasting approaches to life through a collection of essays, letters and other writings attributed to fictional authors. The first volume explores the aesthetic way of life, centred on pleasure, possibility, art and immediate experience. Its best-known sections include discussions of music, tragedy and seduction, alongside the fictional Diary of a Seducer.

The second volume presents the ethical perspective through letters written by Judge William, who argues for commitment, responsibility and continuity in personal life. Marriage, work and deliberate choice are treated as means by which an individual gives shape and meaning to existence. Kierkegaard does not simply resolve the contrast between the aesthetic and ethical positions. Instead, the work uses different voices and forms to confront readers with questions about how a person chooses to live, while also pointing towards religious concerns developed more fully in his later writings.