Soft paternalism or libertarian paternalism has emerged as a new rationality of governing in the UK under New Labour, denoting a style of governing which is aimed at both increasing choice and ensuring welfare. Popularised in Thaler and Sunstein?s best-selling title, Nudge, the approach of libertarian paternalism poses new questions for critical human geographers interested in how the philosophies and practices of the Third Way are being adapted and developed in a range of public policy spheres, including the environment, personal finance and health policy. Focusing specifically on the case of the UK, this article charts how soft paternalism appeals to the intellectual influences of behavioural economics, psychology and the neurosciences, amongst others, to justify government interventions based on the ?non-ideal? or irrational citizen. By identifying the distinctive mechanisms associated with this ?behaviour change? agenda, such as ?choice architecture?, we explore the contribution of behavioural geographies and political geographies of the state to further understanding of the techniques and rationalities of governing.