4 ms·

"Perfect information" is a term of art for games, it doesn't literally mean you are omnipotent.

thom 4y ago
Is it a particularly useful term here? It seems to mean you could theoretically play perfectly but in almost every real situation you can't, which is true of every human activity (including war). Information is hidden by complexity, but it's still utterly inaccessible.
- CogitoCogito 4y ago
  You know the entire state of the chess board. You don’t know the entire state of your enemy forces. I’m both cases information could be said to be hidden by complexity, but in the case of war information is also just plain hidden. Edit: it would be similar to your example of war if you e.g. couldn’t see their pieces or something that would cause information asymmetry. This would make the game very different so clearly the term of art _is_ useful and important.
  - thom 4y ago
    I suppose my problem is that the term 'perfect information' doesn't really communicate anything really interesting about chess. Whereas the equally valid term of art 'incomplete information' actually does, because it captures the fact that you lack knowledge of your opponent's strategy, but nobody ever uses that term. Chess is like navigating a maze or a minefield, it's like stumbling into an ambush. It's much more like war than tic-tac-toe.
    - CogitoCogito 4y ago
      > I suppose my problem is that the term 'perfect information' doesn't really communicate anything really interesting about chess. Yes it _does_ communicate something interesting. It is a basic fact about the rules of play. If there were imperfect information, it would be a different game. Poker with perfect information means everyone plays with their cards up. It is a fundamentally different game. The fact that chess has perfect information for all parties is fundamental to the game.
      - thom 4y ago
        And while I understand that you’re coming at this from a technical standpoint and I can’t argue with the definition, I still think on a human level chess is more like poker than tic-tac-toe (because you’re spending a lot of time imperfectly filling in gaps in information about what your opponent could be up to), and so the category defined by this technical term isn’t so useful in a human conversation such as we’re having, with no prizes from technical correctness. I’m not really interested in repeatedly restating the definition, I’m saying it’s not a good signifier for the differences between chess and war. Maybe that’s not interesting to you, but it is to me as a player and designer of games! And on a deeper level I suppose I’m guilty of exactly the same thing because this is a thread about poetry anyway. :P
        thom 4y ago
        Eh, no longer really enamoured by these thoughts, because that's really what's interesting about almost any game, but somehow I still bristle whenever people bring this up about chess.
nanis 4y ago
Exactly. In particular, "perfect information" means you know all the strategies available to your opponent. You also know that your opponent knows this. And you know that your opponent knows that you know that your opponent knows that you know all the strategies to your opponent ad infinitum symmetrically. In this context, a strategy is a function that maps every history of moves by you and your opponent to an action. So, while chess is theoretically a game of perfect information, in practice it is less so. Real war is not a game of perfect information, because you do not know all the strategies available to your opponent. In addition, you and your opponent's priors may have an intersection of zero measure which makes things very interesting. War is what happens when a certain kind of people try to play the game of chicken which is usually not taught in the kind of fun programs like master's of international studies for members of the preferred party because it is too sophisticated due to the fact that it admits an infinite number of Nash equilibria ... instead, such programs prefer to focus on prisoners' dilemma which, having a dominant strategy equilibrium, is more suitable to ensure such students can go back to the bureaucracy after having passed their classes with perfect As and get us in to war.

thom 4y ago

Is it a particularly useful term here? It seems to mean you could theoretically play perfectly but in almost every real situation you can't, which is true of every human activity (including war). Information is hidden by complexity, but it's still utterly inaccessible.

CogitoCogito 4y ago
You know the entire state of the chess board. You don’t know the entire state of your enemy forces. I’m both cases information could be said to be hidden by complexity, but in the case of war information is also just plain hidden. Edit: it would be similar to your example of war if you e.g. couldn’t see their pieces or something that would cause information asymmetry. This would make the game very different so clearly the term of art _is_ useful and important.
- thom 4y ago
  I suppose my problem is that the term 'perfect information' doesn't really communicate anything really interesting about chess. Whereas the equally valid term of art 'incomplete information' actually does, because it captures the fact that you lack knowledge of your opponent's strategy, but nobody ever uses that term. Chess is like navigating a maze or a minefield, it's like stumbling into an ambush. It's much more like war than tic-tac-toe.
  - CogitoCogito 4y ago
    > I suppose my problem is that the term 'perfect information' doesn't really communicate anything really interesting about chess. Yes it _does_ communicate something interesting. It is a basic fact about the rules of play. If there were imperfect information, it would be a different game. Poker with perfect information means everyone plays with their cards up. It is a fundamentally different game. The fact that chess has perfect information for all parties is fundamental to the game.
    - thom 4y ago
      And while I understand that you’re coming at this from a technical standpoint and I can’t argue with the definition, I still think on a human level chess is more like poker than tic-tac-toe (because you’re spending a lot of time imperfectly filling in gaps in information about what your opponent could be up to), and so the category defined by this technical term isn’t so useful in a human conversation such as we’re having, with no prizes from technical correctness. I’m not really interested in repeatedly restating the definition, I’m saying it’s not a good signifier for the differences between chess and war. Maybe that’s not interesting to you, but it is to me as a player and designer of games! And on a deeper level I suppose I’m guilty of exactly the same thing because this is a thread about poetry anyway. :P
      - thom 4y ago
        Eh, no longer really enamoured by these thoughts, because that's really what's interesting about almost any game, but somehow I still bristle whenever people bring this up about chess.

nanis 4y ago

Exactly. In particular, "perfect information" means you know all the strategies available to your opponent. You also know that your opponent knows this. And you know that your opponent knows that you know that your opponent knows that you know all the strategies to your opponent ad infinitum symmetrically. In this context, a strategy is a function that maps every history of moves by you and your opponent to an action. So, while chess is theoretically a game of perfect information, in practice it is less so. Real war is not a game of perfect information, because you do not know all the strategies available to your opponent. In addition, you and your opponent's priors may have an intersection of zero measure which makes things very interesting. War is what happens when a certain kind of people try to play the game of chicken which is usually not taught in the kind of fun programs like master's of international studies for members of the preferred party because it is too sophisticated due to the fact that it admits an infinite number of Nash equilibria ... instead, such programs prefer to focus on prisoners' dilemma which, having a dominant strategy equilibrium, is more suitable to ensure such students can go back to the bureaucracy after having passed their classes with perfect As and get us in to war.