Peter Singer points out in his marvelous book How Are We to Live? that in our society–in which materialist, consumeristic, individualistic self-interest is paramount–self-interest and an ethical life are seen as being in conflict. However, I would argue that this apparent conflict comes from the contradictory character of our notion of self-interest as well as from its narrowness.
The truth of the matter is that none of us exists on our won; we all exist interdependently in a web of relationships of mutual contingence. Thus, my self-interest includes far more than what the body-mind labeled “Adam” thinks is in his interest; it includes the interests of the other human beings that surround him, of the beings in the ecosystems in which he lives, and of the biosphere on which his life depends. If we broader our sense of self to take into account the multiple relationships of social, physiological, chemical, political, economic, etc. interdependence that our existence relies on, we shall find that an ethical life is a logical consequence of our wider vision. Doing good is best for me, for other beings, and for my world as well.