Peter K. Unger (//; born 1942) is a contemporary American philosopher and professor at New York University. His main interests lie in the fields of metaphysics, epistemology, ethics, and the philosophy of mind. He attended Swarthmore College at the same time as David Lewis, earning a B.A. in philosophy in 1962, and Oxford University, where he studied under A. J. Ayer and earned a doctorate in 1966.
Unger has written a defense of profound philosophical skepticism. In Ignorance (1975), he argues that nobody knows anything and even that nobody is reasonably or justified in believing anything.
In Philosophical Relativity (1984), he argues that many philosophical questions cannot be definitively answered.
In the field of applied ethics, his main work is his 1995 book Living High and Letting Die. There he argues that we have a moral duty to make large donations to life-saving charities (such as Oxfam and UNICEF), and that once we have given all of our own money and possessions, beyond what is needed to survive, we should give what belongs to others, even if we have to beg, borrow, or steal in the process.
In "The Mental Problems of the Many" (2002), he argues for Substantial Interactionist Dualism on questions of mind and matter: that each of us is an immaterial soul. The argument is extended and fortified in his 2006 book All the Power in the World.
In Empty Ideas (2014), he argues that analytic philosophy, being little more than baseless speculation at best, has delivered no substantial results as to how things are with concrete reality.
- Ignorance: A Case for Scepticism (Oxford University Press, 1975 and 2002) ISBN 0-19-824417-7
- Philosophical Relativity (Blackwell and Minnesota, 1984; Oxford, 2002) ISBN 0-19-515553-X
- Identity, Consciousness and Value (Oxford, 1990) ISBN 0-19-507917-5
- Living High and Letting Die: Our Illusion of Innocence (Oxford, 1996) ISBN 0-19-510859-0
- All the Power in the World (Oxford, 2006) ISBN 0-19-515561-0
- Philosophical Papers, Volume 1 (Oxford, 2006) ISBN 0-19-515552-1
- Philosophical Papers, Volume 2 (Oxford, 2006) ISBN 0-19-530158-7
- Empty Ideas: A Critique of Analytic Philosophy (Oxford, 2014) ISBN 978-0-19933081-2
- “An Analysis of Factual Knowledge,” The Journal of Philosophy, LXV (1968): 157-170
- “A Defense of Skepticism,” The Philosophical Review, LXXX (1971): 198-219.
- “The Uniqueness in Causation,” American Philosophical Quarterly, 14 (1977): 177-188.
- “There Are No Ordinary Things,” Synthese, 41 (1979): 117-154.
- "I do not Exist", in Perception and Identity, G. F. MacDonald (ed.), London: Macmillan, 1979 and Material Constitution, Michael C. Rea (ed.), 1996.
- “Why There Are No People,” Midwest Studies in Philosophy, IV (1979): 177-222.
- "The Problem of the Many", Midwest Studies in Philosophy, V (1980), pp. 411‑467.
- “The Causal Theory of Reference,” Philosophical Studies, 43 (1983): 1-45.
- “The Mystery of the Physical and the Matter of Qualities,” Midwest Studies in Philosophy, XXII (1999), 75-99.
- “Minimizing Arbitrariness: Toward Metaphysics of Infinitely Many Isolated Concrete Worlds,” Midwest Studies in Philosophy, IX (1984): 29-51.
- "The Mental Problems of the Many", Oxford Studies in Metaphysics, Volume 1, Oxford, 2002.
- "Free Will and Scientiphicalism", Philosophy and Phenomenological Research, vol. 65 (2002).
- "The Survival of the Sentient", Philosophical Perspectives, vol. 14 (2000).
- "Swarthmore College :: Philosophy :: Department Alumni with PHIL Ph.D.s". Swarthmore College. 2009. Retrieved 2009-03-05.
- "UPI Article: Thinking about life: Peter Unger". UPI. 2001. Retrieved 2011-12-12.
- "NYU > Philosophy > Unger, Peter". New York University. Retrieved 2009-03-05.