The Logic of Scientific Discovery

Logik der Forschung is a 1934 book by Karl Popper. It was originally written in German, but reformulated in English by Popper himself some years later, to be published as The Logic of Scientific Discovery in 1959. This forms the rare case of a major work to appear in two languages, both written by the author instead of being translated. Sir Peter Medawar called it "one of the most important documents of the twentieth century." In it, Popper argued that science proceeds by falsification; that is, no number of experiments can ever prove a theory, but a single experiment can contradict one. Thus, falsifiability is an essential characteristic of any scientific theory.

The German version is currently in print by Mohr Siebeck (ISBN 316148410X), the English one by Routledge publishers (ISBN 0415278449).