- Civis Illustris
Yes, thinking about it now I can see how most uses of the subjunctive either contain, or could have come out of, some idea of potentiality, except for maybe causal clauses. I suppose this could have come from some hypothesized idea of the cause/effect relationship, i.e. Cum X, Y -> "We know Y happened, and maybe X was its cause", but it feels like a stretch...Yes, it's used the way you say in many Latin constructions — as in circumstantial, causal and concessive cum clauses, which all indicate absolutely real facts (purpose is still logically potential, though). But that may be (perhaps, in my idea), a deviation from the original basic meaning of the subjunctive, which I imagine was potentiality.