One way to get the assurance you need to be able to trust someone to keep their part of the bargain is for there to be a mechanism by which sanctions are imposed on those who renege on agreements.  Reverting to our Prisoner's Dilemma, imagine that the revolutionary group that the prisoners belong to has a way of enforcing the agreement between them to cooperate: namely, they will kill the defector. 

The philosopher Thomas Hobbes (1588-1679) thought that the only way out of social situations like this was to have some mechanism which ensured that individuals did not defect, some way of enforcing that agreements or contracts are kept by imposing sanctions on those who break them.  For Hobbes it was the State that was the agency of enforcement, the ‘sword’ in the epigram.  Without the existence of the government and its laws, courts, and police we would all be in a ‘state of nature’, thought Hobbes, essentially structured like a Prisoner's Dilemma, which is a “constant state of war, of one with all” and hence, in his immortal words, “the life of man, solitary, poor, nasty, brutish, and short.”  The heavy fine imposed on those caught watching TV without a license or those caught riding busses for free are relatively trivial examples of the fear of the ‘sword’ producing the public goods.  Can you think of more important ones?  In the eyes of many influenced by Hobbes the need to escape the Prisoner's Dilemma is an argument for the creation of a strong State with the power to enforce agreements. 

But is the ‘sword’ the only way out of the Prisoner's Dilemma?  Perhaps not.  For what if you knew you would be playing the game more than once with the same people?  What if the social situations we find ourselves in are more like an Iterated or Repeated Prisoner's Dilemma than a one-off Prisoner's Dilemma, as many of them certainly seem to be?  Perhaps the trust necessary for cooperation to get off the ground can evolve spontaneously during a series of Prisoner's Dilemmas, especially if punitive behaviour by cooperators is adopted towards defectors.  For defectors’ reputations will be ruined and so no one will trust them in the future and so they may very well not receive the benefits from cooperative interactions in the future. 

According to this line of thought, cooperation early on in a series of Prisoner's Dilemmas makes possible not only the cooperative benefits in that situation but the cooperative benefits in future situations.  So it may be in your self-interest to cooperate after all!  But then escaping the Prisoner's Dilemma does not require an activist State.  Or perhaps it still does require one.  Can you think why?  Or perhaps this is entirely the wrong way of looking at it!  Maybe people are, by their very nature, by and large both trusting and trustworthy.  Indeed, could it be that a general altruistic concern for the well being of others provides sufficient reason for people to cooperate, to keep their agreements?  Or is Hobbes’ more cynical view of human nature as egoistic more true to the facts?  Play the repeated game and see what you think. 

You can learn more about the Prisoner's Dilemma and political philosophy in general by taking the Open University’s course in political philosophy, from which this version of the Prisoner's Dilemma web game is drawn. Click here to view the course details.