The sane answer is that it solves a cooperation problem.
Reciprocal altruism sometimes sends a relatively weak signal—it says that you will cooperate so long as the “shadow of the future” is not too ominous.
Invoking “good” and “evil” signals more that you believe in moral absolutes: the forces of good and evil.
On the one hand, that is a stronger signalling technique—it attempts to signal that you won’t defect—no matter what!
On the other hand, it makes you look a bit as though you are crazy, don’t understand rationality or game theory—and this can make your behaviour harder to model.
As with most signalling, it should be costly to be credible. Alas, practically anyone can rattle on about good and evil. I am not convinced it is very effective overall.
Reciprocal altruism sometimes sends a relatively weak signal—it says that you will cooperate so long as the “shadow of the future” is not too ominous.
Invoking “good” and “evil” signals more that you believe in moral absolutes: the forces of good and evil.
On the one hand, that is a stronger signalling technique—it attempts to signal that you won’t defect—no matter what!
On the other hand, it makes you look a bit as though you are crazy, don’t understand rationality or game theory—and this can make your behaviour harder to model.
As with most signalling, it should be costly to be credible. Alas, practically anyone can rattle on about good and evil. I am not convinced it is very effective overall.