" Sidgwick thinks these judgments give rise to a “dictate of reason,” by which he means that if we were purely rational beings, it would motivate us to action. Human beings are not purely rational beings, so although accepting the dictate of reason will give us a motive to act in the way the maxim of benevolence prescribes, we are likely to have other motives, some of which will support it and some that may conflict with it. Among the supporting motives will be what Sidgwick called “sympathy and philanthropic enthusiasm,” by which he may mean something akin to what today would be called empathy. Among the opposing motives may be racism, nationalism, and egoism. But in a person who sees that it is more rational to aim at the good of all than the good of some smaller group, following one’s own interest and disregarding the interests of others is likely to seem “ignoble.” That will produce a sense of discomfort that Sidgwick calls “the normal emotional concomitant or expression” of the recognition that the good of the whole—that is, of everyone—is to be preferred to the good of the part, that is, oneself. "

― Peter Singer , The Most Good You Can Do: How Effective Altruism Is Changing Ideas About Living Ethically