Jon, List, I don't have time to respond right now. But there are two points that are true for every version of modal logic from Aristotle to the Scholastics to Peirce and to the latest and greatest versions of today:
1. For every version of modal logic, there is some reason WHY certain worlds (or contexts within a world) are possible or necessary or not. 2. The postulates or whatever statements are asserted about that world add that additional information. There is more to say, but those two statements are true. Peirce said a great deal more in many ways about many kinds of possibilities in his many years of MSS, publications, reports, etc. There is no need for him to use the word 'modal' in those discussions. That is implicit. In fact, every branch of science and engineering is about possible interpretations (science) and possible designs (engineering). Every thought about what to do when you or Peirce or anybody else gets up in the morning is a thought about the possible world before you or them. CP has 1072 occurrences of the word 'possible'. Every such sentence is a sentence in modal logic. Any version of modal logic that is adequate for supporting ordinary English must be able to represent all of them. That was the goal for the IKL logic. I believe that was the goal for Peirce's Delta graphs: support the logic necessary for pragmaticism. That implies every version of science, including all the practical sciences -- and daily life. A proof of pragmaticism was the primary goal of Peirce's final decade, and everything he wrote must be evaluated according to its utility in supporting it. John
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