If two things are correlated, there is causation. Either A causes B, B causes A, they have common cause, or they have a common effect you're conditioning on.
That doesn't seem to be strictly true. Of all the things that are correlated it would seem that there would be some that have none of the listed causal relationships. It is merely highly probable that one of those is the case.
That doesn't seem to be strictly true.
It goes against the spirit of "15 words" to insist on strict truth. The merit of the quote lies in the fourth clause.
or they have a common effect you're conditioning on.
That's the big surprise. The point of boiling it down to "15 words" is to pick which subtlety makes it into the shortest formulation.
People want to tell everything instead of telling the best 15 words. They want to learn everything instead of the best 15 words. In this thread, instead post the best 15-words from a book you've read recently (or anything else). It has to stand on its own. It's not a summary, the whole value needs to be contained in those words.
I'll start in the comments below.
(Voted by the Schelling study group as the best exercise of the meeting.)