The prisoner’s dilemma is often claimed to show that people do not have an incentive to cooperate. It is sometimes called the invisible foot because it seems to disprove Adam Smith’s invisible hand metaphor of cooperation. It is then claimed that the state is needed to intervene to force people to cooperate. Khan Academy explains the Prisoners’ Dilemma well in a video titled Prisoners’ Dilemma and Nash Equilibrium.

In a single game of the prisoner’s dilemma individuals do have the incentive to defect rather than cooperate with each other. Yet, if the prisoner’s dilemma is played over and over with an uncertain end time, by the same players, it is called an iterative prisoner’s dilemma. In an iterative prisoner’s dilemma the incentives change so that in order to encourage future cooperation and better gains, players do have an incentive to cooperate. The book The Evolution of Cooperation, by Robert Axelrod records the finding of competitive tournaments involving experts in many disciplines from around the world competing to design the best strategy to win an iterative prisoner’s dilemma. Here is a video that explains the findings.

In the book Robert Axelrod explains how cooperation can and does emerge without a central authority and sometimes in spite of government efforts to get people to kill each other. As in the case of the Christmas truce of World War I.

During World War I, the stalemate of trench warfare resulted in soldiers from both sides being positioned in close proximity to each other, such that they had many repeat interactions with enemy soldiers over a long period of time. Each side learned that if they killed their enemy, the other side would respond by killing some of them, however, if they did not kill their enemy the other side would reciprocate. Eventually, they got so comfortable with each other that they celebrated Christmas by singing carols and playing soccer. The generals had to replace the soldiers in order to get combat to resume. Militaries have since learned not to allow soldiers to stay in the same position for too long to prevent peace from breaking out. Yet, why does cooperation emerge between enemies on the battlefield?

Axelrod took his learnings from the tournaments and other analysis and found the most successful strategy for an iterative prisoner’s dilemma game is TIT-FOR-TAT.

Axelrod outlined how people can best succeed in an iterative prisoner’s dilemma game in a variety of environments:
1- Don’t be envious. Don’t try to take from people just because they have more than you.
2- Don’t be the first to defect. Defect is like aggress.
3- Reciprocate both cooperation and defection. If people cooperate, cooperate with them. If people defect against you, do not tolerate it.
4-Don’t be too clever. Don’t backstab, don’t be unforgiving and be predictable.

So when cooperation emerged on the battlefield in World War I, the soldiers were just playing the TIT-FOR-TAT strategy.

Notice how this strategy looks a lot like the Non-Aggression Principle. That is, don’t be the first to defect, is similar to, do not initiate aggression. We could call TIT-FOR-TAT the Non-Aggression Strategy. Considering the success of the Non-Aggression Strategy, it seems there are consequential reasons to follow the Non-Aggression Principle. That is, applying Non-Aggression as a strategy in situations that are like an iterative prisoner’s dilemma game is more likely to lead to success than other strategies.