On 2009-Dec-3, at 8:42 pm, Jon Lang wrote:
"but" _can_ change existing behavior, but doesn't have to. So "with" becomes the safe version of run-time composition, guaranteeing that whatever you mix in won't disturb existing behavior, and "but" becomes the unsafe version that you can fall back on when you need to change said behavior. [...] I suppose you could allow for both, with the default being "fail on conflict" and an adverb being available to force it to quietly resolve the dispute.
Yes; I guess "but" could have an adverb to control its strictness too, come to that. But not requiring "but" to change behaviour seems reasonable -- I would read it as "but make sure that X", where you want to draw attention to X even though it might technically be redundant.
-David
