Carl Jung was a psychiatrist. In 1950, Emily Blandish quoted him as saying: "Don't you know if you get one hundred of the most intelligent people in the world together, they're a stupid mob? Ten thousand would have the collective intelligence of an alligator." (PROSE: The Tunnel at the End of the Light)
The Third Doctor had an acquaintance named Carl who was a "clever fellow", and coined the term for synchronicity. They had an in-depth discussion about it a few years before he met Sarah Jane Smith. (PROSE: The Ghosts of N-Space [+]Loading...["The Ghosts of N-Space (novelisation)"])
Behind the scenes
Carl Jung indeed discussed synchronicity in Synchronicity: An Acausal Connecting Principle.