Born in Budapest, Hungary. Koestler was educated at the University of Vienna. He was the author of many popular books including Arrow in the Blue, (Volume I of his autobiography), Darkness at Noon (a novel about the evils of the Soviet state), The Yogi and the Commissar (another book about Communism), The Sleepwalkers, The Act of Creation, and The Thirteenth Tribe. In the latter work, Koestler argued that most Jews today are descendants of the Khazars, a people in the Caucasus who adopted Judaism in the 8th century and were later forced to move westwards into current Russia and Poland.
Koestler was fluent in Hungarian, German, and English, and knew some rusty Hebrew. From 1926 to 1929 he lived for a short time in the British Mandate of Palestine. Koestler, an advocate of euthanasia, and suffering from Alzheimer's disease, took his own life along with his wife in a joint suicide in England.
Much of Koestler's work was completely out of step with mainstream views. He did not merely arrive at different answers to common questions. Instead, Koestler answered, or tried to answer, important questions that others were not even asking. Some considered this a sign of his true creative genius.
Koestler's book The Thirteenth Tribe advanced the controversial conclusion that European, or Ashkenazi Jews, are not descended from the Israelites of antiquity, but from a group of Khazars who converted to Judaism in the Middle Ages. Koestler stated that part of his intent in writing the book was to defuse anti-semitism by undermining the identification of European Jews with the Jews of the Bible, rendering anti-semitic epithets like "Christ killer", for example, inapplicable. Ironically, Koestler's thesis that Ashkenazi Jews are not semitic has become an important article of many anti-semitic groups. Some Palestinian advocates have adopted this thesis quite eagerly, since identifying most Jews as non-semitic seriously undermines their historical claims to the land of Israel.
Koestler's own view of Israel was that it would never be destroyed, short of a second Holocaust. He supported the statehood of Israel, but opposed the idea of a diaspora Jewish culture. In an interview in the London Jewish Chronicle, about the time of Israel's statehood, Koestler asserted that all Jews should either migrate to Israel or else assimilate completely into their local cultures.
The result of this originality is a uneven set of ideas and conclusions. Some of his, such as his work on creativity, can be appreciated as brilliant. Some ideas challenge us to readjust our thinking in order to grasp their importance. Other ideas are little more than nonsense. But taken as a whole, they are well worth serious consideration.
The issue of mysticism, while implicit in his works, carried tremendous weight on his personal life. This was confirmed when he left a substantial part of his own estate to establish the Koestler Institute in the University of Edinburgh dedicated to the study of parapsychological phenomena. Such personal belief in the unexplained might have arisen from his political apostasy with regard to his leftist politics, draining himself of the certainty and, perhaps, bravado he once had when he was still a member of the Communist Party.
Always the connoeisseur and lover, Koestler was married three times, excluding the short romantic fling he had with notable French thinker Simone de Beauvoir, probably explaining the mutual animosity between Koestler and Jean-Paul Sartre.
Books by Arthur Koestler