It’s not one I endorse using when what someone has said isn’t right. To the extent that “X, but Y” is understood to mean (not-X and Y) it’s a broken form of communication; to the extent that “X, but Y” is understood to mean (X and Y) it’s false when X is false; to the extent that “X, but Y” is understood to mean (Y and (X or not X)) it is strictly worse than “Y”.
Then again, I once got the feedback at a meeting that I was the only person the speaker knew who could say “Everything you just said is absolutely correct” in a way that left completely unambiguous the implicit ”...and you’re a moron,” so there may well be a huge gap here between what I endorse and my practice. In my defense, though, everything the speaker had just said was absolutely correct. (It was also entirely irrelevant to the thing I’d been talking about.)
It’s not one I endorse using when what someone has said isn’t right.
To the extent that “X, but Y” is understood to mean (not-X and Y) it’s a broken form of communication; to the extent that “X, but Y” is understood to mean (X and Y) it’s false when X is false; to the extent that “X, but Y” is understood to mean (Y and (X or not X)) it is strictly worse than “Y”.
Then again, I once got the feedback at a meeting that I was the only person the speaker knew who could say “Everything you just said is absolutely correct” in a way that left completely unambiguous the implicit ”...and you’re a moron,” so there may well be a huge gap here between what I endorse and my practice. In my defense, though, everything the speaker had just said was absolutely correct. (It was also entirely irrelevant to the thing I’d been talking about.)