Logic of Scientific Discovery, The

The Logic of Scientific Discovery first presented Karl Popper's main ideas on methodology, including falsifiability as a criterion for science and the representation of scientific theories as logical systems from which other results followed by pure deduction. Both ideas are qualified and extended in later works by Popper and his follower Imré Lakatos.

Popper was born in Vienna, Austria, in 1902. During the 1920s, he was an early and enthusiastic participant in the philosophical movement called the Vienna Circle. After the rise of Nazism, he fled Austria for New Zealand, where he spent World War II. In 1949, he was appointed Professor of Logic and Scientific Method at the London School of Economics (LSE), where he remained for the rest of his teaching career. He was knighted by Queen Elizabeth II in 1965. Although he retired in 1969, he continued a prodigious output of philosophical work until his death in 1994. He was succeeded at LSE by his protégé Lakatos, who extended his methodological work in important ways.

The Logic of Scientific Discovery's central methodological idea is falsifiability. The Vienna Circle philosophers, or logical positivists, had proposed, first, that all meaningful discourse was completely verifiable, and second, that science was coextensive with meaningful discourse. Originally, [Page 729]they meant by this that a statement should be considered meaningful, and hence scientific, if and only if it was possible to show that it was true, either by logical means or on the basis of the evidence of the senses. Popper became the most important critic of their early work. He pointed out that scientific laws, which are represented as unrestricted or universal generalizations such as “all planets have elliptical orbits” (Kepler's Second Law), are not verifiable by any finite set of sense observations and thus cannot be counted as meaningful or scientific. To escape this paradox, Popper substituted falsifiability for verifiability as the key logical relation of scientific statements. He thereby separated the question of meaning from the question of whether a claim was scientific. A statement could be considered scientific if it could, in principle, be shown to be false on the basis of sensory evidence, which in practice meant experiment or observation. “All planets have elliptical orbits” could be shown to be false by finding a planet with an orbit that was not an ellipse. This has never happened, but if it did the law would be counted as false, and such a discovery might be made tomorrow. The law is scientific because it is falsifiable, although it has not actually been falsified. Falsifiability requires only that the conditions under which a statement would be deemed false are specifiable; it does not require that they have actually come about. However, when this happens, Popper assumed scientists would respond with a new and better conjecture. Scientific methodology should not attempt to avoid mistakes, but rather, as Popper famously put it, it should try to make its mistakes as quickly as possible. Scientific progress results from this sequence of conjectures and refutations, with each new conjecture requiring the precise grounds of specification for its failure to satisfy the principle of falsifiability. Popper's image of science achieved great popularity among working scientists, and he was acknowledged by several Nobel prize winners (including Peter Medewar, John Eccles, and Jacques Monod).

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