Synchronicity is the experience of two or more events as meaningfully related, whereas they are unlikely to be causally related. The subject sees it as a meaningful coincidence, although the events need not be exactly simultaneous in time. The concept of synchronicity was first described by Carl Gustav Jung, a Swiss psychologist, in the 1920s.
The concept does not question, or compete with, the notion of causality. Instead, it maintains that just as events may be connected by a causal line, they may also be connected by meaning. A grouping of events by meaning need not have an explanation in terms of cause and effect.
The idea of synchronicity is that the conceptual relationship of minds, defined as the relationship between ideas, is intricately structured in its own logical way and gives rise to relationships that are not causal in nature. These relationships can manifest themselves as occurrences that are meaningfully related.
Synchronistic events reveal an underlying pattern, a conceptual framework that encompasses, but is larger than, any of the systems that display the synchronicity. The suggestion of a larger framework is essential to satisfy the definition of synchronicity as originally developed by Carl Gustav Jung.
Jung coined the word to describe what he called "temporally coincident occurrences of acausal events." Jung variously described synchronicity as an "acausal connecting principle", "meaningful coincidence" and "acausal parallelism". Jung introduced the concept as early as the 1920s, but gave a full statement of it only in 1951 in an Eranos lecture and in 1952, published a paper, Synchronizität als ein Prinzip akausaler Zusammenhänge (Synchronicity – An Acausal Connecting Principle), in a volume with a related study by the physicist (and Nobel laureate) Wolfgang Pauli.
It was a principle that Jung felt gave conclusive evidence for his concepts of archetypes and the collective unconscious, in that it was descriptive of a governing dynamic that underlies the whole of human experience and history – social, emotional, psychological, and spiritual. Concurrent events that first appear to be coincidental but later turn out to be causally related are termed incoincident.
Jung believed that many experiences that are coincidences due to chance in terms of causality suggested the manifestation of parallel events or circumstances in terms of meaning, reflecting this governing dynamic.
Even at Jung's presentation of his work on synchronicity in 1951 at an Eranos lecture, his ideas on synchronicity were evolving. Following discussions with both Albert Einstein and Wolfgang Pauli, Jung believed that there were parallels between synchronicity and aspects of relativity theory and quantum mechanics. Jung was transfixed by the idea that life was not a series of random events but rather an expression of a deeper order, which he and Pauli referred to as Unus mundus. This deeper order led to the insights that a person was both embedded in an orderly framework and was the focus of that orderly framework and that the realisation of this was more than just an intellectual exercise, but also having elements of a spiritual awakening. From the religious perspective, synchronicity shares similar characteristics of an "intervention of grace". Jung also believed that in a person's life, synchronicity served a role similar to that of dreams, with the purpose of shifting a person's egocentric conscious thinking to greater wholeness.
A close associate of Jung, Marie-Louise von Franz, stated towards the end of her life that the concept of synchronicity must now be worked on by a new generation of researchers. For example, in the years since the publication of Jung’s work on synchronicity, some writers largely sympathetic to Jung's approach have taken issue with certain aspects of his theory, including the question of how frequently synchronicity occurs. For example, in "The Waking Dream: Unlocking the Symbolic Language of Our Lives", Ray Grasse suggests that instead of being a "rare" phenomenon, as Jung suggested, synchronicity is more likely all-pervasive, and that the occasional dramatic coincidence is only the tip of a larger iceberg of meaning that underlies our lives. Grasse places the discussion of synchronicity in the context of what he calls the "symbolist" world view, a traditional way of perceiving the universe that regards all phenomena as interwoven by linked analogies or "correspondences." Though omnipresent, these correspondences tend to become obvious to us only in the case of the most startling coincidences. The study of astrology, he argues, offers a practical method of not only becoming more conscious of these subtle connections but also of testing and even predicting their occurrence throughout our lives.
One of Jung's favourite quotes on synchronicity was from Through the Looking-Glass by Lewis Carroll, in which the White Queen says to Alice: "It's a poor sort of memory that only works backwards".
'The rule is, jam to-morrow and jam yesterday – but never jam to-day.''It's a poor sort of memory that only works backwards,' the Queen remarked.
'It MUST come sometimes to "jam to-day,"' Alice objected.
'No, it can't,' said the Queen. 'It's jam every OTHER day: to-day isn't any OTHER day, you know.'
'I don't understand you,' said Alice. 'It's dreadfully confusing!'
'That's the effect of living backwards,' the Queen said kindly: 'it always makes one a little giddy at first--'
'Living backwards!' Alice repeated in great astonishment. 'I never heard of such a thing!'
'--but there's one great advantage in it, that one's memory works both ways.'
'I'm sure MINE only works one way,' Alice remarked. 'I can't remember things before they happen.'
The French writer Émile Deschamps claims in his memoirs that, in 1805, he was treated to some plum pudding by a stranger named Monsieur de Fontgibu. Ten years later, the writer encountered plum pudding on the menu of a Paris restaurant and wanted to order some, but the waiter told him that the last dish had already been served to another customer, who turned out to be de Fontgibu. Many years later, in 1832, Deschamps was at a dinner and once again ordered plum pudding. He recalled the earlier incident and told his friends that only de Fontgibu was missing to make the setting complete – and in the same instant, the now senile de Fontgibu entered the room.
In his book Synchronicity (1952), Jung tells the following story as an example of a synchronistic event:
A young woman I was treating had, at a critical moment, a dream in which she was given a golden scarab. While she was telling me this dream, I sat with my back to the closed window. Suddenly I heard a noise behind me, like a gentle tapping. I turned round and saw a flying insect knocking against the window-pane from the outside. I opened the window and caught the creature in the air as it flew in. It was the nearest analogy to a golden scarab one finds in our latitudes, a scarabaeid beetle, the common rose-chafer (Cetonia aurata), which, contrary to its usual habits had evidently felt the urge to get into a dark room at this particular moment. I must admit that nothing like it ever happened to me before or since.
Jung wrote, after describing some examples, "When coincidences pile up in this way, one cannot help being impressed by them – for the greater the number of terms in such a series, or the more unusual its character, the more improbable it becomes."
In the book Thirty Years That Shook Physics – The Story of Quantum Theory (1966), George Gamow writes about Wolfgang Pauli, who was apparently considered a person particularly associated to Synchronicity Events. Gamow whimsically refers to 'The "Pauli effect", a mysterious phenomenon which is not, and probably never will, be understood on a purely materialistic basis. The following anecdote is told:
It is well known that theoretical physicists cannot handle experimental equipment; it breaks whenever they touch it. Pauli was such a good theoretical physicist that something usually broke in the lab whenever he merely stepped across the threshold. A mysterious event that did not seem at first to be connected with Pauli's presence once occurred in Professor J. Franck's laboratory in Göttingen. Early one afternoon, without apparent cause, a complicated apparatus for the study of atomic phenomena collapsed. Franck wrote humorously about this to Pauli at his Zürich address and, after some delay, received an answer in an envelope with a Danish stamp. Pauli wrote that he had gone to visit Bohr and at the time of the mishap in Franck's laboratory his train was stopped for a few minutes at the Göttingen railroad station. You may believe this anecdote or not, but there are many other observations concerning the reality of the Pauli Effect! 
Among some psychologists, Jung's works, such as The Interpretation of Nature and the Psyche, were received as problematic. Fritz Levi, in his 1952 review in Neue Schweizer Rundschau (New Swiss Observations), critiqued Jung's theory of synchronicity as vague in determinability of synchronistic events, saying that Jung never specifically explained his rejection of "magic causality" to which such an acausal principle as synchronicity would be related. He also questioned the theory's usefulness.
In psychology and cognitive science, confirmation bias is a tendency to search for or interpret new information in a way that confirms one's preconceptions, and avoids information and interpretations that contradict prior beliefs. It is a type of cognitive bias and represents an error of inductive inference, or is a form of selection bias toward confirmation of the hypothesis under study, or disconfirmation of an alternative hypothesis. Confirmation bias is of interest in the teaching of critical thinking, as the skill is misused if rigorous critical scrutiny is applied only to evidence that challenges a preconceived idea, but not to evidence that supports it.
Likewise, in psychology and sociology, the term apophenia is used for the apparent detection of a pattern or meaning, in what is actually random or meaningless data. Skeptics, such as Robert Todd Carroll of the Skeptic's Dictionary, argue that the perception of synchronicity is better explained as apophenia. Primates use pattern detection in their form of intelligence, and this can lead to erroneous identification of non-existent patterns. A famous example of this is the fact that human face recognition is so robust, and based on such a basic archetype (essentially two dots and a line contained in a circle), that human beings are very prone to identify faces in random data all through their environment, like the "man in the moon", or faces in wood grain, an example of the visual form of apophenia known as pareidolia.
Although some scientists see potential evidence of synchronicity in areas of research such as quantum theory, chaos theory, and fractal geometry, the concept is not testable by any current scientific method.
The concept of synchronicity is somewhat related to the concept of serendipity.
- Confirmation bias
- Look-elsewhere effect
- Monadology#Controversy in rationalism
- Multiple discovery
- Pratītyasamutpāda Buddhist notion of interdependent co-arising
- Post hoc ergo propter hoc
- Selection bias
- Superluminal communication
- Tarnas, Richard (2006). Cosmos and Psyche. New York: Penguin Group. p. 50. ISBN 0-670-03292-1.
- Koestler, Arthur (1973). The Roots of Coincidence. Vintage. ISBN 0-394-71934-4.
- Jung, Carl (1960). The Structure and Dynamics of the Psyche (Collected Works of C.G. Jung, Volume 8). Princeton, N.J.: Princeton University Press. pp. 417–519. ISBN 0-691-09774-7.
- Casement, Ann, "Who Owns Jung?", Karnac Books, 2007. ISBN 1-85575-403-7. Cf. page 25.
- Jung, Carl G. (1993) . Synchronicity: An Acausal Connecting Principle. Bollingen, Switzerland: Bollingen Foundation. ISBN 978-0-691-01794-5.
- Roderick Main (2000). "Religion, Science, and Synchronicity". Harvest: Journal for Jungian Studies.
- Jung defined the collective unconscious as akin to instincts in Archetypes and the Collective Unconscious.
- In Synchronicity in the final two pages of the Conclusion, Jung stated that not all coincidences are meaningful and further explained the creative causes of this phenomenon.
- Igor V. Limar (2011). "Carl G. Jung’s Synchronicity and Quantum Entanglement: Schrödinger’s Cat ‘Wanders’ Between Chromosomes". NeuroQuantology 09 (2): 313. Archived from the original on 2011-06-30.
- Tarnas, Richard, "Cosmos and Psyche", 2006, Penguin Group, New York, Pgs 50–60
- Grasse,Ray,"The Waking Dream: Unlocking the Symbolic Language of Our Lives", 1996,Quest Books, pages=249–255
- lecture notes, Jung Foundation, New York City, 1980s.
- Through the Looking-Glass, by Lewis Carroll, Ch. 5, Wool and Water.
- Emile Deschamps, Oeuvres completes : Tomes I–VI, Reimpr. de l'ed. de Paris 1872–74
- The Collected Works of C.G. Jung, paragraph 843, Princeton University Press Edition.
- C. G. Jung Jung on Synchronicity and the Paranormal, p. 91
- Thirty Years That Shook Physics – The Story of Quantum Theory, George Gamow, p. 64, Doubleday & Co. Inc. New York, 1966
- Bishop, Paul (2000). Synchronicity and Intellectual Intuition in Kant, Swedenborg, and Jung. The Edwin Mellen Press. pp. 59–62. ISBN 0-7734-7593-1.
- Tim van Gelder, "Heads I win, tails you lose": A Foray Into the Psychology of Philosophy
- Brugger, Peter. "From Haunted Brain to Haunted Science: A Cognitive Neuroscience View of Paranormal and Pseudoscientific Thought", Hauntings and Poltergeists: Multidisciplinary Perspectives, edited by J. Houran and R. Lange (North Carolina: McFarland & Company, Inc. Publishers, 2001).
- Pattern recognition of behavioral events in the nonhuman primate
- Svoboda, Elizabeth (13 February 2007). "Facial Recognition – Brain – Faces, Faces Everywhere". New York Times. Retrieved July, 2010.
- Bishop, pp. 17–20.
- Aziz, Robert (1990). C.G. Jung's Psychology of Religion and Synchronicity (10 ed.). The State University of New York Press. ISBN 0-7914-0166-9.
- Aziz, Robert (1999). "Synchronicity and the Transformation of the Ethical in Jungian Psychology". In Becker, Carl. Asian and Jungian Views of Ethics. Greenwood. ISBN 0-313-30452-1.
- Aziz, Robert (2007). The Syndetic Paradigm: The Untrodden Path Beyond Freud and Jung. The State University of New York Press. ISBN 978-0-7914-6982-8.
- Aziz, Robert (2008). "Foreword". In Storm, Lance. Synchronicity: Multiple Perspectives on Meaningful Coincidence. Pari Publishing. ISBN 978-88-95604-02-2.
- Carey, Harriet (1869). "Monsieur de Fontgibu and the Plum Pudding". Echoes from the Harp of France. p. 174.
- Cederquist, Jan (2010). Meaningful Coincidence. Times Publishing Limited. ISBN 978-0-462-09970-5.
- Combs, Allan; Holland, Mark (2001). Synchronicity: Through the Eyes of Science, Myth, and the Trickster. New York: Marlowe. ISBN 1-56924-599-1.
- Franz, Marie-Louise von (1980). On Divination and Synchronicity: The Psychology of Meaningful Chance. Inner City Books. ISBN 0-919123-02-3.
- Grasse, Ray (1996). The Waking Dream: Unlocking the Symbolic Language of Our Lives. Quest Books. ISBN 0-8356-0749-6.
- Jaworski, Joseph (1996). Synchronicity: the inner path of leadership. Berrett-Koehler Publishers Inc. ISBN 1-881052-94-X.
- Jung, Carl (1972). Synchronicity – An Acausal Connecting Principle. Routledge and Kegan Paul. ISBN 0-7100-7397-6.
- Jung, Carl (1977). Jung on Synchronicity and the Paranormal: Key Readings. Routledge. ISBN 0-415-15508-8.
- Jung, Carl (1981). The Archetypes and the Collective Unconscious. Princeton University Press. ISBN 0-691-01833-2.
- Haule, John Ryan (2010). Jung in the 21st Century: Synchronicity and science. Routledge. ISBN 0-203-83360-0.
- Koestler, Arthur (1973). The Roots of Coincidence. Vintage. ISBN 0-394-71934-4.
- Main, Roderick (2007). Revelations of Chance: Synchronicity as Spiritual Experience. The State University of New York Press. ISBN 0-7914-7024-5.
- Mardorf, Elisabeth. Das kann doch kein Zufall sei (in German).
- Mansfield, Victor (1995). Science, Synchronicity and Soul-Making. Open Court Publishing Company. ISBN 0-8126-9304-3.
- Peat, F. David (1987). Synchronicity, The Bridge Between Matter and Mind. Bantam. ISBN 0-553-34676-8.
- Progoff, Ira (1973). Jung, synchronicity, & human destiny: Noncausal dimensions of human experience. New York, Julian Press. ISBN 0-87097-056-9. OCLC 763819.
- Wilhelm, Richard (1986). Lectures on the I Ching: Constancy and Change Bollingen edition. Princeton University Press; Reprint. ISBN 0-691-01872-3.
- Roth, Remo, F., Return of the World Soul, Wolfgang Pauli, C.G. Jung and the Challenge of Psychophysical Reality [unus mundus]. Pari Publishing, 2011
- Igor V. Limar (2011). Carl G. Jung’s Synchronicity and Quantum Entanglement: Schrödinger’s Cat ‘Wanders’ Between Chromosomes. NeuroQuantology Journal, 09 (2). pp. 313–321.