I had been thinking about a rule syntax of the form A -> (B -> (C -> D)) where A is some source, B is some (non-optional) condition, C is some (optional) condition and D is some outcome. This then let’s us define a meta-rule of the form Value(D) -> A -> (B -> C), so developing arguments about interventions.
That step works (as long as we define pure Epistemic arguments as A -> (B -> (
The problem comes with the nature of “->”. Here, we are confalting the Toulmin style sense of ‘warrants’ (in that A ‘warrant s’ the fact that B -> (C -> D) with the implication C -> D. There’s also the fact that B doesn’t warrant the C -> D in the sam way as A does.
I think the solution is to change to A -> B1 & B2 -> C, where B2 is the optional bit. As a result, gets replaced by blank (which feels better). The only problem is that there is now no difference between B1 and B2, apart from convention - a case of syntax dictating semantics. Bad if you’re Roman, liveable with (I guess) if you’re English.