Walter Sinnott-Armstrong (born 1955) is an American philosopher. He specializes in ethics, epistemology, and more recently in neuroethics, the philosophy of law, and the philosophy of cognitive science. He is the Chauncey Stillman Professor of Practical Ethics in the Department of Philosophy and the Kenan Institute for Ethics at Duke University. He earned his Ph.D. from Yale University under the supervision of Robert Fogelin and Ruth Barcan Marcus, and taught for many years at Dartmouth College, before moving to Duke.
His Moral Skepticisms (2006) defends the view that we do not have fully adequate responses to the moral skeptic. It also defends a coherentist moral epistemology, which he has defended for decades. His Morality Without God? (2009) endorses the moral philosophy of his former colleague Bernard Gert as an alternative to religious views of morality.
In 1999, he debated William Lane Craig in a debate titled "God? A Debate Between A Christian and An Atheist".
Walter Sinnott-Armstrong argues that God is not only not essential to morality, but moral behaviour should be independent of religion. A separate entity, one could say. He strongly disagrees with several core ideas: that atheists are immoral people; that any society will become like lord of the flies if it becomes too secular; that without morality being laid out in front of us, like a commandment, we have no reason to be moral; that absolute moral standards require the existence of a God-he holds that people themselves are inherently good and not bad; and that without religion, we simply couldn't know what is bad and what is good.
Walter Sinnott-Armstrong is a proponent of Contrastivism, the idea that all claims of reasons are relative to contrast classes. According to him, "[the contrastivist] approach applies to explanation (reasons why things happen), moral philosophy (reasons for action), and epistemology (reasons for belief), and it illuminates moral dilemmas, free will, and the grue paradox."