That's a central part of philosophy, of ethics. What do I owe to strangers? What do I owe to my family? What is it to live a good life? Those are questions which we face as individuals.

Not only does his principle justify different treatment for different interests but it allows different treatment for the same interest when diminishing marginal utility is a factor. He is a major proponent of biocentrism. Among the more important human interests are those in avoiding pain in developing one's abilities in satisfying basic needs for food and Peter Singerlter in enjoying warm personal relationships in being free to pursue one's projects without interference "and many others".

In 2004 he was recognised as the Australian Humanist of the Year by the Council of Australian Humanist Societies and in June 2012 was named a Companion of the Order of Australia for his services to philosophy and bioethics. He was voted one of Australia's ten most influential public intellectuals in 2006.