When we make ethical judgments, we must go beyond a personal or sectional point of view and take into account the interests of all those affected, unless we have sound ethical grounds for doing otherwise. This means that we weigh interests, considered simply as interests and not as my interests, or the interests of people of European descent, or of people with IQs higher than 100. This provides us with a basic principle of equality: the principle of equal consideration of interests. The essence of the principle of equal consideration of interests is that we give equal weight in our moral deliberations to the like interests of all those affected by our actions. This means that if only X and Y would be affected by a possible act, and if X stands to lose more than Y stands to gain, it is better not to do the act. We cannot, if we accept the principle of equal consideration of interests, say that doing the act is better, despite the facts described, because we are more concerned about Y than we are about X. What the principle really amounts to is: an interest is an interest, whoever's interest it may be.
Peter Singer, Practical Ethics
ethics, interests, utilitarianism