[7stud]

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Every time you play a hand differently from the way you would have played it if you could see all your opponents' cards, they gain

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This theorem holds true if we may one critically important extra assumption: given all information revealed, people would play in mathematically optimal ways.


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Most of the time, I think that's incorrect. Morton's theorem shows there are some exceptions to the Fundamental Theorem in multiway pots, but the Fundamental Theorem holds true in heads up play.

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I don't think Sklansky is saying this Pokey.
All he is saying is that if you can see all the cards then there is a mathematically optimal way to play.
Not that if you can see all the cards then your play will be optimal. Which seems to be what you are suggesting he says.

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As bitter&twisted said, if you can see the cards, then you can determine the mathematically optimal play. However, if a person can see the cards, but he can't determine the mathematically optimal play, or he can't bring himself to make the mathematically correct play, then he loses and you gain. By definition, if you don't make the mathematically optimal play, you lose. I believe all the fundamental theorem of poker is saying is that there is a mathematically optimal play when all the cards are known, and anytime you deviate from that optimal play, you lose.

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you'll quickly realize that common folks simply do NOT always make the mathematically correct choices.

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All the examples you gave are of people making bad plays. How does that prevent them from losing and the house or their opponent from winning?

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Encouraging mistakes is definitely a good thing, but to say that any time our opponents know our cards AUTOMATICALLY makes their moves optimal seems erroneous at the small-stakes tables.

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The Fundamental Theorem does imply that your opponent's will pay optimally if they can see your cards. However, that doesn't mean they will win if they deviate from the mathematically optimal play. For instance, if someone will fold pocket Kings to your raise preflop because they don't want to risk that much of their bankroll on one hand, it doesn't mean they don't lose if they make the same play when you show them your pocket Queens before you raise. Yet, they played the same way when they didn't know your cards as when you showed them your cards.

So, I guess a strict literal reading of the fundamental theorm could lead you to conclude that your opponent isn't losing by folding his pocket Kings because he played the same way when he could see your cards, but hopefully you can see why that's not true.