You only have to hang around the world of social science research- or policy-related blogging for a few hours before you come across someone willing to snottily inform you, or some other luckless interlocutor, that although the finding of this or that paper may appeal to you, nevertheless don’t you know that Correlation Is Not Causation. Often this seems to be the only thing they know about statistics.
I grudgingly admit that it’s a plausible-sounding rule, and in the textbooks and stuff. But, to be honest, I read it too many times in various posts and comments threads the other day, and in my raging pique I found myself thinking that the next time it happened I would say, “That’s completely backwards: in fact, causation is just correlation” and fling a copy of Hume’s first Enquiry at their head. Or at the screen, I suppose, but that image is less satisfying, because now who’s the crank on the internet, etc.