Sir Karl Raimund Popper (28 July 1902 – 17 September 1994)

Sir Karl Raimund Popper  (28 July 1902 – 17 September 1994) was an Austrian-British philosopher and professor. He is generally regarded as one o.f the greatest philosophers of science of the 20th century
Karl Popper was born in Vienna (then in Austria-Hungary) in 1902, to upper middle-classparents. All of Karl Popper's grandparents were Jewish, but the Popper family converted toLutheranism before Karl was born, and so he received Lutheran baptism.
Popper left school at the age of 16 and attended lectures in mathematics, physics, philosophy, psychology and the history of music as a guest student at the University of Vienna. In 1919, Popper became attracted by Marxism and subsequently joined the Association of Socialist School Students. He also became a member of the Social Democratic Workers' Party of Austria, which was at that time a party that fully adopted the Marxist ideology. After the street battle in the Hörlgasse on 15 June 1919, when police shot eight of his unarmed party comrades, he became disillusioned by what he saw to be the "pseudo-scientific" historical materialism of Marx, abandoned the ideology, and remained a supporter of social liberalism throughout his life.
In 1928, he earned a doctorate in psychology, under the supervision of Karl Bühler. His dissertation was entitled "Die Methodenfrage der Denkpsychologie" (The question of method in cognitive psychology). In 1929, he obtained the authorisation to teach mathematics and physics in secondary school, which he started doing. He married his colleague Josefine Anna Henninger (1906–1985) in 1930. Fearing the rise of Nazism and the threat of the Anschluss, he started to use the evenings and the nights to write his first book Die beiden Grundprobleme der Erkenntnistheorie (The Two Fundamental Problems of the Theory of Knowledge). He needed to publish one to get some academic position in a country that was safe for people of Jewish descent. However, he ended up not publishing the two-volume work, but a condensed version of it with some new material, Logik der Forschung (The Logic of Scientific Discovery), in 1934. Here, he criticised psychologism, naturalism, inductionism, and logical positivism, and put forth his theory of potentialfalsifiability as the criterion demarcating science from non-science. In 1935 and 1936, he took unpaid leave to go to the United Kingdom for a study visit.^[