This paper uses Geoffrey Rose’s theory of population health change to identify that part of lack of resolution of the harm reduction debates emerges from the philosophical question of the possibility of group-level causation. Group-level causation, otherwise known as the supervenience of higher levels onto lower levels, has been a core matter of philosophical and ethical debate. This paper argues that there, the public health standard depends crucially on the contextual environment rather than the individual product’s intrinsic properties. Interpretation of the benefits or the harms of e-cigarettes or other harm reduction products depends on the often unstated assumptions of the potential policy and cultural environments in which e-cigarettes exist, as well as the separate debate over the absolute or relative level of harm of e-cigarettes. Unfortunately, most of the research conducted will not contribute to our understanding of the potential impact of e-cigarettes until we focus on the potential changes to the social and political environment.