1.1 Initiation into the behavioural state The emerging behavioural state: promise, pressure or phantom? How confident is present-day government? Not too confident, it would seem. Solving public problems is generally seen as an arduous challenge. Our late modern society doesn't lend itself to be 'engineered'. It has only become more uncertain, complex, and 'liquid' (Bauman 1999) than before (e.g. Beck 1992; Giddens 1998). This acknowledgement of complexity reflects how today's policymakers think, 'see' and act. They commonly acknowledge that some policy issues have become 'wicked' (Head 2008): so convoluted and contested-both substantively and procedurally, empirically and normatively-that they can at best be 'tamed'. Also, today's policymakers-part of the New Public Governance paradigm-generally realize that they are heavily dependent on other societal actors to get things done and that forging strong and unified public-private networks is far from easy. So they buckle up, strengthen their tolerance for uncertainty and nonperformance, and confess that public problem-solving simply isn't easy. And yet, in the past two decades a policy trend has emerged that goes in the opposite direction of a modest state. This trend has given birth to a type of state that seems all too confident about its ability to shape society. This confidence is drawn from the opportunities discovered by recent advances in the behavioural sciences. A body of 'behavioural insights' (e.g. Dolan et al. 2010; OECD 2017; Lourenço et al. 2016) has developed rapidly, showing how humans often don't make decisions in wholly rational, but often more automatic ways. These insights have given rise to an unorthodox policy style, which subtly intervenes in the everyday spaces of society based on rigorous behavioural analyses and experiments (e.g.