Abraham Lincoln used to ask a certain riddle: If people decided to call a horse's tail a leg, how many legs would horses have?
The answer is, of course, four, because deciding to call a horse's tail a leg doesn't make it a leg. But it's perhaps revealing that a late 19th c. American lawyer would think of this. Pragmatically, in the language game one could play as if one played no other, if the expected answer was five, then five would be the correct answer. There, social norms govern the meaning. We've decided that certain things are quarks and opossums, and certain other things aren't, and these are our ways.
But this is why it becomes important that (late 19th c./early 20th c.) pragmatism is a species (or perhaps a descendant) of idealism, not empiricism. The ability to shift the language norm comes from the fact that the idea itself (that there is a thing called a horse) governs the positivist, empirical, long-settled, ultimately meaning-giving horse-leg-counting process. And that idea can be changed. The change in the idea would be the thing that governed the change in the normative constraints on speech, not some private contract as to language use. When social norms make changes in language use (in ways not directly governed by personal power), it is because something is revealed by the new usage that seems more valuable than the work the old usage was doing.
So, to sort of bring this together, Abe is right. If everyone decided to change a norm within a language, precisely because the scheme was sufficiently plastic to do this, the idea must be the source of the meaning, and not the long-settled empirical processes of verification. They simply wouldn't be able to do it without a more convincing idea. Without a vision, the people perish.
Perhaps.