Carl Jung (1875-1961), synchronicity & the collective unconscious
Carl Jung was a Swiss psychiatrist and colleague of Freud's who broke away from Freudian psychoanalysis over the issue of the unconscious mind as a reservoir of repressed sexual trauma which causes all neuroses. Jung founded his own school of analytical psychology.

Jung believed in astrology, spiritualism, telepathy, telekinesis, clairvoyance and ESP.  In addition to believing in a number of occult  and paranormal notions, Jung contributed two new ones in his attempt to establish a psychology rooted in occult and pseudoscientific beliefs: synchronicity and the collective unconscious.

Synchronicity is an explanatory principle; it explains "meaningful coincidences" such as a beetle flying into his room while a patient was describing a dream about a scarab. The scarab is an Egyptian symbol of rebirth, he noted. Therefore, the propitious moment of the flying beetle indicated that the transcendental meaning of both the scarab in the dream and the insect in the room was that the patient needed to be liberated from her excessive rationalism. His notion of synchronicity is that there is an acausal principle that links events having a similar meaning by their coincidence in time rather than sequentially. He claimed that there is a synchrony between the mind and the phenomenal world of perception.

What evidence is there for synchronicity? None. Jung's defense is so inane I hesitate to repeat it. He argues that "acausal phenomena must exist...since statistics are only possible anyway if there are also exceptions" (1973, Letters, 2:426). He asserts that "...improbable facts exist--otherwise there would be no statistical mean..."  (ibid.: 2:374). Finally, he claims that "the premise of probability simultaneously postulates the existence of the improbable" (ibid. : 2:540).

Even if there were a synchronicity between the mind and the world such that certain coincidences resonate with transcendental truth, there would still be the problem of figuring out those truths. What guide could one possibly use to determine the correctness of an interpretation? There is none except intuition and insight, the same guides that led Jung's teacher, Sigmund Freud, in his interpretation of dreams. The concept of synchronicity is but an expression of apophenia.

According to psychiatrist and author, Anthony Storr, Jung went through a period of mental illness during which he thought he was a prophet with "special insight." Jung referred to his "creative illness" (between 1913-1917) as  a voluntary confrontation with the unconscious. His great "insight" was that he thought all his patients over 35 suffered from "loss of religion" and he had just the thing to fill up their empty, aimless, senseless lives: his own metaphysical system of archetypes and the collective unconscious.

Synchronicity provides access to the archetypes, which are located in the collective unconscious and are characterized by being universal mental predispositions not grounded in experience. Like Plato's Forms (eidos), the archetypes do not originate in the world of the senses, but exist independently of that world and are known directly by the mind. Unlike Plato, however, Jung believed that the archetypes arise spontaneously in the mind, especially in times of crisis. Just as there are meaningful coincidences, such as the beetle and the scarab dream, which open the door to transcendent truths, so too a crisis opens the door of the collective unconscious and lets out an archetype to reveal some deep truth hidden from ordinary consciousness.

Mythology, Jung claimed, bases its stories on the archetypes. Mythology is the reservoir of deep, hidden wondrous truths. Dreams and psychological crises, fevers and derangement, chance encounters resonating with "meaningful coincidences," all are gateways to the collective unconscious, which is ready to restore the individual psyche to health with its insights. Jung maintained that these metaphysical notions are scientifically grounded, but they are not empirically testable in any meaningful way. In short, they are not scientific at all, but pseudoscientific.

... seize the magic!