Published in two volumes in 1843, Either/Or (original Danish title: Enten-Eller) is an influential book written by the Danish philosopher Søren Kierkegaard, exploring the aesthetic and ethical "phases" or "stages" of existence.
Either/Or portrays two life views, one consciously hedonistic, the other based on ethical duty and responsibility. Each life view is written and represented by a fictional pseudonymous author, the prose of the work depending on the life view being discussed. For example, the aesthetic life view is written in short essay form, with poetic imagery and allusions, discussing aesthetic topics such as music, seduction, drama, and beauty. The ethical life view is written as two long letters, with a more argumentative and restrained prose, discussing moral responsibility, critical reflection, and marriage. The views of the book are not neatly summarized, but are expressed as lived experiences embodied by the pseudonymous authors. The book's central concern is the primal question asked by Aristotle, "How should we live?"
Kierkegaard left Copenhagen in October 1841 to spend the winter in Berlin. Although the main purpose of this visit was to attend lectures by German philosopher Friedrich Wilhelm Joseph Schelling, the lectures turned out to be a disappointment for Kierkegaard and many others. During his stay, Kierkegaard worked on the manuscript for Either/Or and returned to Copenhagen in 1842 with draft of the manuscript, which was completed near the end of 1842 and published in February 1843.