PS: A similar point was made by another contributor, in a parallel related discussion on the KBF email list, who distinguished between two purposes:
...noting that “in practice there is often a tradeoff between the explanatory and persuasive aspects of the underlying logic”
- to model a situation to better understand it and programme around it
- to simplify a complex situation to help explain it to others and persuade them of the logic of your proposed intervention (e.g. for funding).
- Evaluability Assessments - Achieving Better Evaluations Nicola Dawkins, 2005 PowerPoint