The Logic of Scientific Discovery

The Logic of Scientific Discovery is a work by Karl Popper first published in 1934. It was originally written in German under the title Logik der Forschung and, some years later, Popper rewrote it in English, appearing in 1959 as The Logic of Scientific Discovery. It is an unusual case of an important work written by the same author in two languages rather than translated. The book became widely known and was published in Spanish in 1962.

Its central thesis is that science should be guided by falsifiability. For Popper, no number of experiments can definitively confirm a universal theory, since a new case may always contradict it; a single reproducible result that refutes it, however, is enough to discard it. The procedure of refutation follows a deductively valid modus tollens, whereas confirmation amounts to affirming the consequent, an invalid form of reasoning. Popper thus proposes falsifiability as the criterion for distinguishing scientific theories from those that are not.

The work had a broad reception. It was much debated by philosophers such as Thomas Kuhn, and its critique of verificationism in logical positivism was regarded as especially influential. Over time, the model also drew objections regarding actual scientific practice, yet it remains a basic reference in discussions of scientific method.