We are strange people. Genetic relatedness leading to cooperation is a common phenomenon. Cooperation with genetically unrelated strangers is not a common phenomenon. Do we expect cooperation from the strangers in the hope of reciprocal altruism? Why do we want to reward people when we know that it is going to cost us? We sometimes become out-of-proportion selfish. We are not afraid of behaving selfishly even for small returns. We willingly punish people even if the punishment proves costly and yields no material gain. We call it ‘altruistic punishment’. Why do we cooperate? Do we cooperate for the sake of others or our own sake? A living organism, to protect itself, needs to protect the environment it lives in. If there is a mismatch between the self and the environment, the chances of survival of either or both are threatened. The conflicts can be resolved when either or both compromise to ensure their survival. One of his friends once asked Mahatma Gandhi if his serving the poor purely humanitarian. He said, “I am here to serve myself only, to find my self-realization through the service of others.” Often, altruists become selfish for their survival. In the struggle for existence, an eternal battle between good and bad, between altruists and the selfish is going on. If one ever leaves the field, the other will not find meaning in existence. Selfishness, after all, is not that bad. One selfish doesn’t like the other selfish. David Sloan Wilson’s research says that selfish individuals have their incentives to get rid of other selfish individuals within their group. ‘Selfish punishers’ use other altruists to punish other selfish individuals. Selfish punishers, however, try to prevent altruists from being eliminated from the group. Within the group, the altruistic behaviour of individuals are vulnerable to exploitation by more selfish individuals, but groups of altruists can robustly defeat more selfish groups. Altruism can, therefore, evolve by natural selection, as long as its collective advantage outweighs its more local disadvantage. Wilson says that punishment is a form of altruism. Consider, for example, a situation where you are largely responsible to put a criminal in jail. This altruistic act of yours results in the punishment of the crooked and brings relief to many law-abiding citizens. But you paid the cost. This is a ‘higher-order public good problem’; someone pays the cost, the benefit of which goes to someone else. Such high order altruists allow themselves to be exploited. Wilson showed in his analysis that the individuals most likely to cheat are also most likely to punish other cheaters. It simply means that the best groups might be those that include a few devils along with the angels.