Counterfactual notation
From Jos Lehmann (University of Amsterdam):
Jos Lehmann noticed potential ambiguity in the notation used for counterfactual propositions. Capital letters, like "A" or "B," are sometimes used to denote propositional variables, and sometimes to denote propositions. For example, in the function A = C (Model M, page 209) "A" stands for the variable "whether rifleman-A shoots", and takes on values in {true, false}, while in statements S1-S5 (page 208), A stands for a proposition (e.g., "Fireman-A shot").