Many of the central doctrinal and policy debates in American environmental law rest, fundamentally, on disagreements over a single empirical question: what motivates firms in their interactions with the environmental regulatory system? The traditional view sees firms as polluters - self-interested economic and political actors, whose rational pursuit of their self-interest guides both their compliance decisions and their attempts to influence policy. To induce compliance, then, environmental enforcement must aim to deter violations through the imposition of penalties; likewise, to prevent firms from capturing the regulatory process, regulation must rely on prescriptive rules and must eschew informal or ad hoc policymaking methods. Reformers, on the other hand, challenge the traditional view. They look at that same deterrence- and rule-based environmental regime and see a complex, ossified system that often makes compliance difficult and impractical, and conclude that much noncompliance with environmental regulation is inadvertent. For these reasons, reformers advocate a more cooperative and collaborative, and less adversarial and punitive, regulatory process. The conflict between these two views casts a long shadow over American environmental regulation. This article has three objectives. First, it traces the numerous and sometimes elusive connections between current doctrinal and policy debates in environmental law (debates over civil and criminal enforcement as well as regulatory reform) and their common root, this question of the accuracy and validity of the rational polluter model. Second, it examines the latest thinking and evidence on this question from legal and social science scholarship, and concludes that the traditional view fails to explain the behavior of many regulated firms. Finally, it argues (using evidence from behavioral psychology and elsewhere) that over-reliance on the rational polluter model may pose a long-term risk to the legitimacy of the American regulatory system, particularly if it fails to meet the expectations of the political moderates.