I'm fond of John McIntyre's language blog on the Baltimore Sun, and I approve of his recent blogpost arguing that the word hopefully can be used as a sentence adverb (read the post here).
My father used to rail against the use of hopefully when, in his opinion, people should have been saying it is to be hoped that. I naïvely agreed, but not wholeheartedly because his six-word replacement was horribly unwieldy and I was just starting to understand that being correct wasn't always right. Now McIntyre has succinctly pointed out that hopefully isn't even wrong.
McIntyre makes his case the subtle way, simply by using other examples of sentence adverbs. While I agree with his argument, I'm not sure that all his examples stand up. I'm willing to be corrected, but I don't think it's a sentence adverb if the adverb can be attached to the verb without changing the meaning, because that would make it just an ordinary adverb displaced from its usual position next to the verb.
So, @ArrantPedantry's example, “Surprisingly, some people still hold to that rule, but thankfully their numbers seem to be dwindling” cannot be changed to "their numbers seem to be dwindling thankfully". That's a proper sentence adverb alright*. True, a comma before thankfully would restore the original meaning, but only by severing the adverb from the verb again.
But what about the other examples?
"Stubbornly, this superstition refuses to go away" can easily be changed to "This superstition stubbornly refuses to go away", so that's not a sentence adverb.
"Sadly, no amount of explanation suffices to wipe it out" can't be changed to "No amount of explanation sadly suffices to wipe it out", so that is a sentence adverb.
"Foolishly, Strunk and White perpetuates it" can certainly be changed to "Strunk and White foolishly perpetuates it". So again, that's not a sentence adverb, though I admire McIntyre's determination that Strunk and White is the shorthand name for a book and therefore singular, although I'd be inclined to use an ampersand there, just to make it clearer.
"Laughably, people follow it unthinkingly" definitely can't be reorganised as "People laughably follow it unthinkingly", so that is a sentence adverb.
I'll forgive McIntyre's final sentence: "Plainly, sentence adverbs, adverbs that modify an entire clause, do exist in English, and oddly, other than hopefully, cause no uproar when they appear," because he would never write such an awkward sentence unless he were deliberately making a point. But it does demonstrate an argument I made in an earlier post about commas: their numbers proliferate when writers try to control the anarchy of a poorly constructed sentence (see The Riot Police Of Punctuation).
Six commas in a 24-word sentence is too much. If I were doing my Sentence Doctor thing, I'd rewrite it as follows:
"Sentence adverbs – adverbs that modify an entire clause – plainly do exist in English. And yet, oddly, only hopefully causes uproar when it appears."
The one sentence has become two, and four of the six commas have gone; two being replaced by en-dashes (if I were American I'd have used em-dashes without spaces). I have also replaced the negative with a positive. Of course, that would negate the point that McIntyre was trying to make, but it's all grist to my mill for grinding indigestible grains of language into the sweet bread of communication.
Moral: An adverb can be a slippery thing, but that's part of the fun
*One of these days I'll blog about why I think 'alright' is perfectly alright, but bear with me for now.