Coincidence

A coincidence is a remarkable concurrence of events or circumstances which have no apparent causal connection with each other. The perception of remarkable coincidences may lead to supernatural, occult, or paranormal claims. Or it may lead to belief in fatalism, which is a doctrine that events will happen in the exact manner of a predetermined plan.

From a statistical perspective, coincidences are inevitable and often less remarkable than they may appear intuitively. An example is the birthday problem, which shows that the probability of two persons having the same birthday already exceeds 50% in a group of only 23 persons.

The first known usage of the word is from c. 1605 with the meaning "exact correspondence in substance or nature" from the French coincidence, from coincider, from Medieval Latin coincidere. The definition evolved in the 1640s as "occurrence or existence during the same time", and again in the writings of Sir Thomas Browne as "a concurrence of events with no apparent connection" around the 1680s.

Swiss psychiatrist Carl Jung developed a theory which states that remarkable coincidences occur because of what he called "synchronicity," which he defined as an "acausal connecting principle."

The Jung-Pauli theory of "synchronicity", conceived by a physicist and a psychologist, both eminent in their fields, represents perhaps the most radical departure from the world-view of mechanistic science in our time. Yet they had a precursor, whose ideas had a considerable influence on Jung: the Austrian biologist Paul Kammerer, a wild genius who committed suicide in 1926, at the age of forty-five.

Arthur Koestler, The Roots of Coincidence

One of Kammerer's passions was collecting coincidences. He published a book titled Das Gesetz der Serie (The Law of Series), which has not been translated into English. In this book he recounted 100 or so anecdotes of coincidences that had led him to formulate his theory of seriality.

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