In this sixteenth issue of our Ideas in American Policing series, Professor James J. Willis of George Mason University examines the relationship between the science of policing and the craft of policing. Over the last century, the police have been the object of almost continuous attempts at reform. Currently, one of the most powerful forces for transforming the police is the evidence-based policing movement. Unlike past reforms, this puts scientific research squarely in the driver’s seat of police decision making. However, improvements in policing rest heavily on the shoulders of those who do policing at the coalface, and patrol officers have long thought of the way they perform their work not as a science but as a craft. Not much attention has focused on how scientific and craft knowledge might contribute to one another in mutually supportive ways, and yet any attempt to improve police performance must take into account the views of those who constitute any department’s largest resource.This essay considers what a true marriage of craft and science might look like for guiding the decisions of rank-and-file officers in two domains relevant to police practice: (1) advancing knowledge about what works and (2) making decisions about the right thing to do.In doing so, it hopes to illuminate some possibilities for reform that policymakers, practitioners, and researchers might consider in their efforts to improve the police of the future.