Take pi (3.14159...) and raise it to the fourth power; then add that to the value of pi raised to the fifth power. The total (403.428...) is exceedingly close to e (2.71828...) raised to the sixth power. Coincidence? Sure, in the sense that two things have "coincided", i.e., come together. But what kind of coincidence is this?

About 15 years ago a friend (JB) and I tried to come up with a taxonomy of coincidences --- or at least some useful categories to describe such things. We never finished or properly wrote it up ... but as an interim snapshot, here are some examples of our system:

Of course, what's "deep" to one observer may be transparently obvious to another. Over time, a coincidence may shift from one class to another, as people understand it better. And some coincidences may belong in multiple bins, depending on how they're viewed or analyzed.

So what other categories of coincidence should be added to the above? (see CorrelationsAndCausality and CoincidentalTaxonomy2)

TopicScience - 2001-10-19

Hmmm. Coincidence may be that we don't yet understand the correlation. I am suspicious of a greater piece of unknown information whenever I hear the word coincidence. Take the randomness of galaxies, stars. I see solar systems as big atoms and infinity as more about size than time. Judy Decker

Many years ago I read The Roots of Coinsidence by Aldous Huxley. It gave me pause to think about what we call the "real" or physical world and what it's made of. Then I stubbed my toe and came back to my senses.

(correlates: PaulHolbrook, PartyLines, QuarterJinx, ...)