Theories of change are essential components of development programming. Yet they are often the last to be developed in the programme cycle – an afterthought to justify activities which have already been planned or to satisfy donor imperatives. This policy memo by Alex de Waal, Aditya Sarkar, Sarah Detzner and Ben Spatz, refocuses attention on the theory of change as a first step to thinking about how and why we think certain actions and strategies will produce desired change or achieve specific policy outcomes.