The State and Social Investigation in Britain and the United States addresses the historical development of the knowledge base upon which the public policies of the democratic state depend. This comparative study stretches from the Enlightenment origins of the impulse to base legislation on scientific knowledge to the twentieth-century development of specialised institutions and professions engaged in social investigation and public policy-making. It probes investigators’ biases and omissions as well as their strengths as factors shaping social learning. It illuminates the vital link between social empiricism and the late nineteenth-century emergence of the New Liberalism in both Britain and the United States. And it ponders the impact on social investigation and social policy today of relativism, antistatism, devolution and privatisation as these currents have developed in both societies since the 1970s.