Realist evaluation is based on a conception of public policies as interventions that produce their outcomes through mechanisms that are only triggered in specific contexts. The analysis of these links between contexts, mechanisms and outcomes is therefore at the heart of this approach. This approach can be based on a variety of methods, but will in all cases use qualitative methods to investigate the mechanisms involved. Belonging to the family of theory-based evaluations, realist evaluation aspires to produce middle range theories that will facilitate the transfer of the knowledge produced on the intervention under study to other contexts or other interventions of the same type.