Søren Kierkegaard's Concluding Unscientific Postscript, ascribed to a pseudonymous author named “Johannes Climacus,” is the source of the notorious claim that “truth is subjectivity.” That alone has provoked a variety of divergent interpretations of the work as a whole, from the time of its publication in February 1846 until the present day. Yet the Postscript has been both celebrated and condemned under many other descriptions: as the chief inspiration for twentieth-century existential thought, as a subversive parody of philosophical argument, as a prelude to later phenomenology, as a critique of mass society, as a forerunner of postmodern relativism, and as a testimonial for Christianity conceived in either theologically conservative or radically progressive terms. For a book that sold only about fifty copies during the first few years after its publication, it has caused quite a stir in the long run.

The Postscript was regarded by Kierkegaard as a culminating work – although he later came to view it as more of a turning point in his authorship – and, as a result, it resembles a sort of “container into which all of the important ideas he has ever had must be crammed.” Philosophers have appropriated and opposed various claims endorsed in the Postscript, which seems more like a philosophical treatise in form and content than perhaps any other work in Kierkegaard's corpus.