In accounts of institutional change, discursive institutionalists point to the role of economic and political ideas in upending institutional stability and providing the raw material for the establishment of a new institutional setup. This approach has typically entailed a conceptualization of ideas as coherent and monolithic and actors as almost automatically following the precepts of the ideas they hold and support. Recent theorizing stresses how ideas are in fact composite and heterogeneous, and actors pragmatic and strategic in how they employ ideas in political struggles. However, this change of focus has until recently not included how foundational ideas of a polity, often referred to as 'public philosophies', are theorized to impact on institution building. Drawing on French Pragmatic Sociology, and taking as a starting point recent efforts within discursive institutionalism to conceptualize the dynamic nature of public philosophies, this paper seeks to foreground moral justification in accounts of ideational and institutional change. It suggests that public philosophies are reflexively used by actors in continual processes of normative justification that may over time produce significant policy shifts. The empirical relevance of the argument is demonstrated through an analysis of gradual ideational and institutional change in French labour market policy, specifically the development from the state-guaranteed minimum income scheme of 1988 to the neoliberal make-work-pay logic of the 2009 scheme, Revenu de solidarité active. The analysis shows that public and moral justifications have underpinned and gradually shaped these radical changes.