It is now generally accepted that the roots of our ethics lie in patterns of behavior that evolved among our pre-human ancestors, the social mammals … - Peter Singer

My students often ask me if I think their parents did wrong to pay the $44,000 per year that it costs to send them to Princeton. I respond that paying that much for a place at an elite university is not justified unless it is seen as an investment in the future that will benefit not only one’s child, but others as well. An outstanding education provides students with the skills, qualifications, and understanding to do more for the world than would otherwise be the case. It is good for the world as a whole if there are more people with these qualities. Even if going to Princeton does no more than open doors to jobs with higher salaries, that, too, is a benefit that can be spread to others, as long as after graduating you remain firm in the resolve to contribute a percentage of that salary to organizations working for the poor, and spread this idea among your highly paid colleagues. The danger, of course, is that your colleagues will instead persuade you that you can’t possibly drive anything less expensive than a BMW and that you absolutely must live in an impressively large apartment in one of the most expensive parts of town.

We do not have to make self- sacrifice a necessary element of altruism. We can regard people as altruists because of the kind of interests they have rather than because they are sacrificing their interests.

The principles of ethics come from our own nature as social, reasoning beings.