Sir Karl Raimund Popper CH FBA FRS (28 July 1902 – 17 September 1994) was an Austrian-British philosopher and professor. He is generally regarded as one of the greatest Philosophers of Science of the 20th Century.
In political discourse, he is known for his vigorous defence of liberal democracy and the principles of social criticism that he came to believe made a flourishing "open society" possible. His political philosophy embraces ideas from all major democratic political ideologies and attempts to reconcile them: social democracy, classical liberalism and others. Popper supported Market Economies but disagreed with major aspects of Libertarianism, he wrote:
We must construct social institutions, enforced by the power of the state, for the protection of the economically weak from the economically strong. (Karl Popper) 
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