Prisoner's Dilemma is a game used to study both social and economic research. You can read more on it on Wikipidia or in Stanford Encyclopedia of Philosophy.

Interestingly, it seems that either:

  1. These two sources are not consistent in how they spell it
  2. They change spelling depending on context in a way I do not grasp

For instance on Wikipedia we have

The prisoner's dilemma is a standard example of a game [...]

and then

Prisoner's Dilemma tournaments have been held [...]


The structure of the traditional Prisoner's Dilemma can be generalized [...]

Similarly in Stanford Encyclopedia of Philosophy we have:

A closely related view is that the prisoner's dilemma game [...]

and then

[...] take the Prisoner's Dilemma to say something important [...]


[...] story suggests that the Prisoner's Dilemma also occupies [...]

It seems that on Wikipedia lower case spelling dominates, while in in Stanford Encyclopedia of Philosophy both versions are used interchangeably.

I would expect it might be correct to use upper case spelling for games matching the definition or for the original version of the game and lower case for variations on it or when more general sense is meant.

That is, we can write

In Golden Balls contestants are presented with prisoner's dilemma

because we mean type of situation in general.

And we can write

This game is a proper instance of Prisoner's Dilemma

meaning that this games matches the definition the specific Prisoner's Dilemma.

However, the abovementioned examples do not seem to comply understanding nor to any other that I could see.

So do these two source spell Prisoner's Dilemma correctly?

And how should we spell it?

  • 3
    We Brits seem to have made up our minds in recent decades (as with so many similar terms, eventually we drop the capitals once the usage becomes sufficiently familiar). Americans seem to be still making up their minds, but I think any attempt to infer a different meaning based on capitalization is just spurious. Commented Sep 25, 2016 at 19:05
  • There's no difference at all. There is no original version of the "game". It is a logical deductive process.
    – Lambie
    Commented Sep 25, 2016 at 20:22
  • 1
    Google Ngram Viewer seems give the same answer for American English - prisoner's dilemma it is, at least starting from the 90s. Thanks!
    – Legat
    Commented Sep 26, 2016 at 19:46
  • @FumbleFingers You Brits don't have a monopoly on ... wait... maybe you do...wait again...actually looking at all those graphs together makes me think that in both BrE and AmE there's roughly the same usage of both (but that brits talk about them more either way).
    – Mitch
    Commented Oct 26, 2016 at 22:29
  • @Legat It seems to be in free variation. It started off in caps, but then with familiarity lost the caps sometimes. Which one to do is a style choice at this point unless some style guide specifies.
    – Mitch
    Commented Oct 26, 2016 at 22:36

2 Answers 2


A proprietorial, commercial game such as Scrabble or Cludo, needs capitals. For how long it legally needs capitals depends on copyright law; how long idiomatically or socially needs capitals depends on who is asked…

A traditional game such as chess or draughts or checkers doesn't strictly need capitals, but no-one's going to complain if capitals are used through personal preference.

  • Interesting answer, I only wonder if there are any non-proprietorial / non-commercial games that have their names capitalized anyway?
    – Legat
    Commented Oct 23, 2016 at 23:13
  • Yes, Legat, there doubtlessly are… and don't you think they're covered by "such as chess or draughts or checkers"? Did I miss something there? Commented Oct 26, 2016 at 21:38
  • 1
    @RobbieGoodwin The Prisoner's Dilemma was never a commercial game. It is a thought experiment or theoretical modeling problem. It's capitalization is more on par with Fundamental Theorem of Arithmetic vs fundamental theorem of arithmetic
    – Mitch
    Commented Oct 26, 2016 at 22:41
  • Oh… thanks, Mitch. If there are rules within the particular subject - yes, like your F/fundaments… - then I suppose those take precedence over general language Commented Oct 27, 2016 at 8:59
  • Chess, draughts and checkers aren't examples of non-propetorial games that are capitalized.
    – Legat
    Commented Oct 28, 2016 at 1:59

Prisoner's Dilemma is a concept of game theory that has 'a misleading name taken from one example' (Derek Parfit, Reasons and Persons, sect. 2.3). Most of its applications have nothing to do with prisoners; the fictional example that originally introduced the concept did involve prisoners, but in a contrived, precisely defined setting that was unlikely to ever be encountered by real-life prisoners. While the name may be confusing to the uninitiated, it has become far too well established in the literature for anybody to try to change it.

Its being a technical term, of course, does not in itself necessitate that Prisoner's Dilemma be capitalised. The decision of many writers to capitalise it is probably due to their wanting to make sure that their readers will, upon seeing the term so printed, immediately think of the theoretical concept, and not have the slightest inclination to think of any of the various other dilemmas that a prisoner might encounter, which could all be called (lowercase) prisoner's dilemmas. This may often be helpful to the readers and that justifies the practice. On the other hand, the readers who are well familiar with the concept may not need that help, which may justify not capitalising the term when writing for them.

(The other answer posted on this page is based on a misunderstanding of what constitutes a game in this context. The decision whether to capitalise Prisoner's Dilemma has nothing to do with intellectual-property law.)

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