Walter Sinnott-Armstrong is an American philosopher. He specializes in ethics, moral psychology, neuro-ethics, the philosophy of law, epistemology, the philosophy of religion, and informal logic.

He is Chauncey Stillman Professor of Practical Ethics in the Department of Philosophy and the Kenan Institute for Ethics at Duke University. He earned his PhD from Yale University under Ruth Barcan Marcus and Robert Fogelin, and taught for many years at Dartmouth College, before moving to Duke.

Walter Sinnott-Armstrong has a secondary appointment Duke Law School and is core faculty in the Duke Institute for Brain Sciences, the Duke Center for Cognitive Neuroscience, and the Duke Center for Interdisciplinary Decision Sciences. He serves as Resource Faculty in the Philosophy Department of the University of North Carolina at Chapel Hill, Partner Investigator at the Oxford Centre for Neuroethics, and Research Scientist with The Mind Research Network in New Mexico. He has visited at the National Institutes of Health, National Cheng Kung University in Taiwan, and the Macquarie Research Center for Agency, Values, and Ethics in Australia. He has received fellowships from the Harvard Program in Ethics and the Professions, the Princeton Center for Human Values, the Oxford Uehiro Centre for Practical Ethics, the Center for Applied Philosophy and Public Ethics at the Australian National University, and the Sage Center for the Study of the Mind at the University of California, Santa Barbara. He has been co-chair of the Board of Officers of the American Philosophical Association and co-director of the MacArthur Law and Neuroscience Project. He earned his Bachelor’s degree from Amherst College and his doctorate from Yale University.

He has published widely on ethics (theoretical and applied as well as meta-ethics), empirical moral psychology and neuroscience, philosophy of law, epistemology, philosophy of religion, and informal logic. Most recently, he is the author of Morality Without God? and Moral Skepticisms as well as editor of Moral Psychology, volumes I-V. His articles have appeared in a variety of philosophical, scientific, and popular journals and collections. He teaches a popular MOOC named Think Again on the Coursera platform.

His current work is on moral psychology and brain science as well as uses of neuroscience in legal systems. He is working on one book on scrupulosity, another book on how to overcome polarization, and a third book that will develop a contrastivist view of freedom and responsibility.