The concept of public action is a magnifying lens for shedding light on the plurality of institutional and social actors interacting in policies. Taking into account a changing social world that is redefining the State and its instruments, it is well suited for picking out transformations that have been affecting European social policies for some twenty years or so now: the territorial reorganization of powers; the spread of a public-private mix in the provision of services; the rise of new forms of collaborative governance; the institutionalization of the European agenda on social...