A central question in law and economics is how people will behave in the presence of legal rules. An essential part of that inquiry is what makes people happy or unhappy – what increases or decreases their “subjective well-being.” There is ample evidence that individuals make decisions based in part on what they believe will improve their well-being. In order to understand how legal rules will influence behavior, it is thus vital to understand how those rules will affect happiness. More generally, viewing law through a hedonic lens can help legal policymakers determine whether (or not) a given law or policy will be beneficial for the individuals affected by it. Jonathan S. Masur is John P. Wilson Professor of Law, David and Celia Hilliard Research Scholar, and Director of the Wachtell, Lipton, Rosen & Katz Program in Behavioral Law, Finance and Economics. The 2018 Coase Lecture in Law and Economics was presented on February 6, 2018.