Synchronicity

Synchronicity was, according to the Third Doctor, "the principle that a coincidence may happen without any causal link and yet still be significant". He made this observation in relation to the fact that the Brigadier and Sarah happened to be in Sicily simultaneously. The Doctor went on to say that many schools of philosophy were based upon synchronicity. When the Brigadier suggested that synchronicity was essentially the notion of pre-destination, the Doctor basically agreed, saying that fatalism was a cruder expression of the same idea. (AUDIO: The Ghosts of N-Space ^[+]Loading...["The Ghosts of N-Space (audio story)"])

The term was originally coined by a "clever fellow" named Carl, with whom the Third Doctor was personally acquainted. This man cited the I Ching as one example of a philosophical system based on this phenomenon. (PROSE: The Ghosts of N-Space ^[+]Loading...["The Ghosts of N-Space (novelisation)"])

The Second Doctor once told Jamie McCrimmon that it was synchronicity that the TARDIS always arrived somewhere there was a problem. (PROSE: The Age of Ambition ^[+]Loading...["The Age of Ambition (short story)"])

Behind the scenes

The "Carl" in question, referenced in The Ghosts of N-Space ^[+]Loading...["The Ghosts of N-Space (novelisation)"], is Carl Jung.