The Prisoner’s Dilemma is a concept used to model a strategic interaction in which actors choosing their behaviors rationally according to their own self-interest make everyone worse off than they could have been otherwise. This particular “game” is used both to understand failures of cooperation such as arms races and ethnic warfare and to prescribe particular solutions designed to elicit cooperation. The key feature of the game is that, when the game is played only once, no matter what another player does (cooperating with me or trying to exploit me), I am better off trying to exploit the other player – so in the end, every player exploits rather than cooperates, and they are all worse off than they would have been could someone have “forced” them to cooperate. What has been less often analyzed, to my knowledge, is the ethics of the Prisoner’s Dilemma game.
Whether one has a duty to cooperate with others in Prisoner’s Dilemma-like situations is an important question both for policy and for daily life. Take the question of one’s duties toward the environment. The environment is in many aspects a public good subject to Prisoner’s Dilemma problems. Clean air, clean water, and biodiversity are benefits that we all enjoy, and from which non-contributors cannot feasibly be excluded. Therefore, people have an incentive to take less care of the environment than they would could the environment be privatized. Whether other people “do their part” or not, I’m better off not trying to contribute.
So let’s take some examples of things one could do for the benefit of the environment: eating less meat; polluting less by, e.g., driving less; propagating native species and destroying invasive species; reducing, reusing, and recycling; not littering; not spraying pesticides. Assume for the sake of argument that we will all benefit if everyone did these things. Do we then have a duty to do them? Would it be wrong not to do them?
I’ll derive my view from a very simple starting point: One has a duty not to exploit others, but one does not have a duty to allow oneself to be exploited. In the simple Prisoner’s Dilemma game, each player has only two options: cooperate (and be exploited) or defect (and exploit). In real life, however, there are different gradations of action, from, e.g., walking or riding a bicycle everywhere to driving a Hummer. Moreover, cooperation isn’t actually zero, and therefore cooperation doesn’t always entail being exploited. These considerations imply that some degree of cooperation in Prisoner’s Dilemma situations might actually be morally mandatory, but that devoting your life to providing public goods for others would not be.
Now, the latter part of the starting point could be made even stronger. Let’s say that not only does one not have a duty to allow oneself to be exploited, but one does not have a general duty to sacrifice one’s own interests for the benefit of others. Then, the benefits of the existing scheme of mutual cooperation, including your own, must be greater to you, individually, than the costs of your individual contribution, for that contribution to be morally mandatory. To see this, suppose it were otherwise. Suppose that your efforts on behalf of the environment, say, actually made you worse off than you would be if no one did what you did, including yourself. If that were the case, then you would be making yourself worse off for the benefit of others. That would count as a praiseworthy and supererogatory sacrifice, but not a moral requirement.
So here are my tentative conclusions. If your efforts, combined with the really existing efforts of everyone else, make you better off (taking opportunity costs into account) relative to a situation in which no one undertakes effort, then you have a moral duty to make those efforts. To do otherwise would be to free-ride on the efforts of others and thus to exploit them, which is wrong. If this condition is not satisfied, however, you do not have a duty to contribute – but it would still be praiseworthy to do so, unless the effort is clearly hopeless, in which case the impartial observer is more likely to have pity on your madness than praise for it. I actually think this is a rather strong conclusion and implies that we have a duty to undertake some (but not extraordinary) positive action on behalf of the environment, for instance. What remains interesting and unusual about the Prisoner’s Dilemma is that it models a set of cases for which the rightness of one person’s actions apparently depends on what others are doing.