Martin E. P. Seligman, PhD, Director of the Penn Positive Psychology Center, Zellerbach Family Professor of Psychology in the Penn Department of Psychology, and Director of the Penn Master of Applied Positive Psychology program (MAPP). Seligman is a leading authority in the fields of Positive Psychology, resilience, learned helplessness, depression, optimism and pessimism. He has written more than 275 scholarly publications and 25 books, including Flourish: A Visionary New Understanding of Happiness and Well-being (2011) and co-authored Character Strengths and Virtues: A Handbook and Classification (Oxford University Press 2004). Peter Railton, PhD, is Gregory S. Kavka Distinguished University Professor of Philosophy at University of Michigan, Ann Arbor. Railton has worked in the philosophy of science, ethics, metaethics, political philosophy, and aesthetics. He has also taught at Berkeley and Princeton and been affiliated with various research centers in the US and Europe. Roy F. Baumeister, PhD, is Frances Eppes Eminent Scholar and Professor of Psychology at Florida State University. Baumeister's research spans self and identity, self-regulation, interpersonal rejection and the need to belong, sexuality and gender, aggression, self-esteem, meaning, and self-presentation. He has written over 500 publications and 31 books, including Willpower: Rediscovering the Greatest Human Strength (2011) and The Cultural Animal: Human Nature, Meaning, and Social Life (Oxford University Press 2005). Chandra Sripada, MD, PhD, is Associate Professor of Philosophy and Psychiatry at University of Michigan, Ann Arbor. Sripada studies brain mechanisms of decision-making, prospection, and self-control, and tries to understand how emerging results from the sciences impact our picture of ourselves as free and rational agents.