The social domain has seen a growing debate on the effectiveness of public measures. The realization is taking shape that the legitimacy of social policies - such as the socialization of vulnerable groups, anti-radicalization programs or regeneration projects in deprived neighbourhoods - has to go beyond the intuition that they "should" work. But unlike methods in spheres such as medicine and healthcare, social programs typically have no sharp demarcation in time, intensity or target group and are implemented in a rich context of unforeseen and unknown variables. This makes it difficult (if not impossible) to assess their impact with research methods that centralize a mono causal effect. In The Plausibility of Policy Vasco Lub presents alternative approaches to assessing the likelihood to which social policy measures achieve their intended effects. One of his main lines of argument is to confront policy assumptions with existing scientific data. In doing so he sheds light on how such measures can be assessed and to what degree claims about those intended effects can be substantiated.