Assumptions in theories of change

This paper argues that assumptions in a theory of change are the causal connections, events, and conditions that need to be realized for the intervention to work. Using an example of an intervention aimed at improving educational outcomes for girls in a conservative region, two kinds of assumptions are discussed: cause-effect assumptions and causal-link assumptions. Implications for the use of theories of change, including their use in setting causality and the utility of evidence in argument for learning about and testing assumptions are also discussed. The need for an explicit description of what is meant by the term ‘assumptions’ in association with a theory of change is also highlighted. •Assumptions in a ToC are the causal connections, events and conditions that need to be realized for the intervention to work.•Cause-effect assumptions imply a causal relationship, typically between one result and another, or an activity and a result.•Causal link assumptions are about what events and conditions are needed or likely needed for a causal link to be.•It is important to be clear on which cause-effect assumptions or aggregates of assumptions are being addressed.•The approach taken needs to be based on the specific causal issue being explored and the situation at hand.