In 1840 Soren Kierkegaard became engaged to Regine Olsen, and within a year he broke the engagement off, a decision he never fully explained and that friends and family found bewildering given his evident continuing feelings for her. What followed was one of the strangest bodies of work in philosophy: rather than write in his own voice, Kierkegaard began publishing under a series of invented authors, Johannes Climacus, Victor Eremita, Johannes de Silentio among them, each given a distinct personality, style, and philosophical position, so that his books argue with each other as much as they argue a single thesis.
Either/Or, published in 1843, stages the aesthetic and ethical ways of living against each other through invented editors and letters; Fear and Trembling, published the same year under the name Johannes de Silentio, wrestles with the biblical story of Abraham and Isaac to ask what it would mean to suspend ordinary ethics for an individual, absolute relationship to God.
Scholars have long read the broken engagement as one key to why Kierkegaard needed these masks: writing pseudonymously let him explore positions, including ones he ultimately rejected, from the inside, without claiming any single one as his settled personal view, a method suited to his larger argument that becoming a genuine self is a task each individual must work out in their own existence rather than a truth that can simply be handed to them from outside. He signed his final religious writings under his own name, treating the pseudonymous project as, by then, complete.