Section 8 Soft arithmetic is also the answer to understanding causal maps

In section 6 I claimed that in order for our causal maps to be of any use to anyone, we need to, at least sometimes, attempt to make comparisons between different elements, and comparisons of comparisons, like “B is more important for E than C is”. This amounts to being able to assign some kind of numerical quantities to elements of the maps, so that we can make deductions with our maps following rules which I call “soft arithmetic”. In lots of occasions we won’t be sure enough to be able to make any such statements, but in others the evidence is so strong that we wouldn’t be doing our job if we didn’t.

Then in section 7 I claimed that we need rules for understanding causal maps: how do we turn causal information from stakeholders into features in a diagram, and in reverse, how do we read a diagram to decode the causal information. I argued that the best way to agree or understand these translation rules for causal maps is to show how to make deductions with them. Just as we don’t waste time in primary school explaining what “+” means; instead we show how to use it.

So it won’t be a surprise if I now point out the obvious: the two claims are one and the same, and the two sets of rules are one and the same. The rules we will look at in the following sections will tell us both how to do “soft calculations” with causal maps and tell us what the elements mean, so that we can encode causal information into maps and back again.