All Thinkers

Thinkers Timeline

Key thinkers across history — grouped by era, colour-coded by discipline. Click any card to explore ideas, quotations, and classroom contexts.

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Modern — 1800 to 1950
Ludwig Wittgenstein 1889-1951 · Austria-Hungary / United Kingdom
Ludwig Wittgenstein was an Austrian-British philosopher. Many consider him the greatest philosopher of the twentieth century. He was born on 26 April 1889 in Vienna, Austria, into one of the wealthiest families in the Austro-Hungarian Empire. His father was a powerful steel industrialist. His mother was a gifted musician. The family home was visited by composers like Brahms and Mahler. Three of his brothers died by suicide. Ludwig was first trained as an engineer in Berlin and Manchester, where he worked on aeroplane design. While studying, he became fascinated by the foundations of mathematics. In 1911 he travelled to Cambridge to work with the philosopher Bertrand Russell, who quickly recognised his genius. When the First World War broke out in 1914, Wittgenstein volunteered for the Austro-Hungarian army. He fought bravely and was decorated. While at the front and in a prisoner-of-war camp, he wrote his first book. That book, the Tractatus Logico-Philosophicus, was published in 1921. He believed it had solved all the major problems of philosophy. He gave away his vast inherited fortune and became a primary school teacher in remote Austrian villages. He also designed an austere house for his sister in Vienna. In 1929 he returned to Cambridge, having decided his earlier work contained serious mistakes. He spent the rest of his life developing a very different philosophy. He served as a hospital porter during the Second World War. He died of prostate cancer in Cambridge on 29 April 1951, aged 62. His last words to his housekeeper were: 'Tell them I've had a wonderful life.'
"The limits of my language mean the limits of my world."
Karl Popper 1902-1994 · Austria / United Kingdom
Karl Popper was an Austrian-British philosopher of science and politics. He was born in 1902 in Vienna into a well-off, secular Jewish family that had converted to Lutheran Christianity. His parents loved books, and Popper grew up reading widely. As a young man he tried out many of the big intellectual movements of his time. He attended Marxist meetings, studied Freudian psychology, and worked briefly with the Adlerian school of psychology. He was struck by something that bothered him for the rest of his life. The followers of these movements seemed able to explain everything. Whatever happened in the world, Marxism, Freudianism, and Adlerian theory could fit it into their system. Popper began to wonder whether this was a strength or a weakness. He trained as a teacher and earned a doctorate in philosophy from the University of Vienna in 1928. In 1934 he published his first major book, Logic of Scientific Discovery, which made his name in philosophy of science. As Hitler rose to power, Popper, with his Jewish background, knew he had to leave Europe. In 1937 he took a teaching post in New Zealand. There, during the Second World War, he wrote The Open Society and Its Enemies, his great defence of liberal democracy. In 1946 he moved to the London School of Economics, where he stayed for the rest of his career. He was knighted in 1965. He wrote on philosophy of science, politics, the mind, and many other subjects. He died in 1994 in London at the age of 92.
"A theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice."