My wife and I went to an Indian restaurant for a yummy dinner and a glass of wine. At one of the tables I recognize a face.
"Hey, isn't that TexasLimitKing, one of the most successful online players in the world?"
TexasLimitKing - something of an unperson, who has kept a very low profile despite huge triumphs at the highest stakes in online poker. His photo has probably only appeared once, in a glossy poker magazine a couple of months earlier.
I remember faces, but I'm not sure about this one. It's hard to look glossy after two months of fall darkness. Still I'd bet 3-1 on the hypothesis that I'm having chicken masala alongside a living poker legend. That's my prior probability.
Meanwhile, my wife finds all this extremely interesting.
A word here and there from the other table reaches across the small room; it's always about poker. This fact ought to strengthen my hypothesis but on the other hand, who doesn't talk poker these days?
Then I recognize another face at the same table. It's Ramzi Jelassi, one of the players in Team Gnuf. I told you I remember faces.
This piece of data, on the contrary, is significant. Having dinner with Jelassi must be clearly more likely for a fellow poker pro than for an arbitrary person. Reversed probability.
I'd say, with this new data, the probability that TexasLimitKing is present has risen to at least 95%. That's my posterior probability, and as such it's not bad.
So how do I act based on this quasi-knowledge? Do I walk up to the table and ask TexasLimitKing to stake me in the WSOP? Do I sit down at his table and whine over bad beats at the NL50 tables? Do I try to teach him the latest ploy in poker strategy?
Nothing of the sort, of course. I let him eat his chicken tikka in peace. Hey, I'm no paparazzo, and for all I know he may still be someone else completely.
My wife complains that I keep remembering faces - even when I've demonstrably never seen the person before. She's right, probably.
On the other hand, how can I be certain that's even my wife sitting there? Sure, I recognize her face, but then again...