What is theory of change? What is program logic?

‘Intervention logic’ is the term commonly used in New Zealand for program logic. I have been musing a lot recently over the definitions and whether there is any difference in the names. I realize that people do use the terms interchangeably but some people draw clear distinctions for  each. But for me, I notice that program logic/ intervention logic are used a lot by evaluators. Evaluators are often using this tool to clarify an existing program, hence they work bottom up - from the activities up to the outcomes. They call the stuff in the middle intermediate outcomes as they are on their way upwards. Evaluators do from time to time end up using program logic for planning, then they might map downwards. But I think most would be more used to map upwards.

However, theory of change is nearly always mapped downwards. Starting at the outcomes we identify the necessary preconditions to achieve the outcomes .(We call the stuff in the middle preconditions rather than intermediate outcomes) . At the end of the day the models might look very similar, but the thinking process is quite different! Backwards mapping from the outcome down does make one’s head hurt more! Its much more of a planning tool than a clarification tool. So there you go, I add my distinction to the rest of them!