Research on the role of ideas has contributed greatly to our understanding of processes of policy change. The article suggests that theories that deal with interest-driven reform processes might also benefit in important ways from including ideas as a variable in their models. Arguing that ideas are useful to power-seeking actors, the article develops a theory about the nature of ideas that emphasises the dynamic and open-ended relation between actors and ideas: actors can use different strategies to affect ideas to work in their interest, but because of their intersubjective nature, ideas have a life of their own and are never fully controllable. Analysing the case of the Danish jobcentre reform it is demonstrated how ideas may be introduced by actors in order to promote their interests, but actors must use ideas with due attention to the historical background of the idea as well as which other ideas can be associated with them, both in present and future policy processes. In this way ideas create – with their dynamic nature – both possibilities and limits for power-seeking actors.