The realization that there is (a) a double coincidence of wants and (b) this can be solved with some sort of currency are absolutely questions already answered

The realization that there is (a) a double coincidence of wants and (b) this can be solved with some sort of currency are absolutely questions already answered if not intuitively than explicitly by money in modern society, as are related concepts like debt and interest. When someone talks about the double coincidence of wants being a myth, they are not referring to the obvious fact that this is a problem money solves, but that this reason, alone or primarilty, is the reason money, as a world-historical concept, came to be in all societies.