I'm rather busy with work right now, so maybe now's a good time to ramble about not-fully-formed thoughts. This kind of writing takes less effort because I don't need to do research for it, and readers are invited to do most of the thinking.
In Sam Harris' book, The Moral Landscape, the eponymous landscape is basically a metaphor for a utility function. If we as a society make certain choices, that will put us somewhere on this landscape, and our height determines how good the outcome is. To Sam Harris, morality means finding the highest peaks on the landscape, and going there.
Sam Harris' metaphor exemplifies the view that morality is a calculation. Figure out what we want, figure out the best way to achieve it, and that's moral.
In everyday practice, morality often seems to serve a different function. Here are actions I do on a regular basis that I consider to have moral character: I clean dishes after using them, instead of leaving the task to others. I try to recycle as much as possible. I try to be polite and make my coworkers feel comfortable. All of these I do not because they benefit me, but primarily because they benefit others.
The fact of the matter is that we are always trapped in prisoner's dilemma (or similar games) of varying sizes. If I didn't wash the dishes, that would save me time, but cause more work for others. If none of us washed dishes, the sink would get dirty. Appealing to morality is a way to motivate people to cooperate. If someone doesn't cooperate, morality also offers us a mechanism to punish or shame them.
Now the tricky thing is, cooperation is not moral in every prisoner's dilemma. Here are some examples:
1. It is not moral for corporations to cooperate with each other by raising prices together. This can be argued from a utilitarian perspective, since the cooperation helps corporations, but causes greater harm to consumers.
2. Often it's not morally obligatory to give up property or our self-autonomy just because it might help someone else. We tend to place special value on rights like these.
3. We don't consider it immoral for a nation to have a military. If every nation has a military of equal strength, this is worse than the world where no one wastes resources on it. Yet the world where no nation has a military is unrealistic, so we don't expect nations to be cooperative to that degree.
Can you think of other situations where cooperation in prisoner's dilemma is not necessarily moral?