crucially

Since I began working in theoretical linguistics several years ago, I've been struck by a specific usage of the word "crucially". In common parlance, we typically use "crucial" to mean "absolutely necessary" or "the best course of action". We might say "It's crucial that we arrive before midnight", perhaps because the road closes at that time. But I'd say the adverbial form is less common. COCA returns 15344 hits for "crucial" and 417 for "crucially", for a ratio of 37:1 in favor of the adjective. On the other hand, "quick" returns 33060 hits, and "quickly" returns 61284, showing the adverbial form is significantly more common, with a ratio of 2:1 in favor of the adverb. In scientific parlance, on the other hand, "crucially" is typically used to indicate a piece of data that shows beyond a reasonable doubt that the argument goes through. As an abstract example, let's say we want to show that the numeral "one" is more common than the numeral "two" -- in all languages. We compare a number of languages, and all but language X show "one" with a higher frequency than "two". This goes against our argument, unless we can show a specific reason why we would expect "two" to be more frequent in language X in a way that does not predict this in the other languages. We might say "Crucially, the numeral 'two' in language X forms a part of the common idiom 'blah blah blah'". This crucial piece of data shows that language X does not form a counterexample.

I was interested in seeing if this use of crucially (or rather, the overwhelming commonality of using "crucially" when relating an argument) was specific to theoretical linguistics, or if other fields also present arguments this way. To examine this, I did a text search for "crucially" in the New England Journal of Medicine (non-social science), Natural Language & Linguistic Theory (theoretical linguistics), International Journal of American Linguistics (less theoretical linguistics), Political Behavior (non-linguistic social science), and Philosophical Issues (non-science). NEJM returned 19 articles in the past 10 years, for a rate of around 2/yr. NLLT returned 198 in the past 28 years, for a rate of around 7/yr. IJAL returned 23 for the past 18 years, for a rate of around 1/yr. PB returned 10 for 1979-2007, a rate of less than 1 every 2 years. PI returned 212 for 1991-1998, a rate of over 30/yr. My inability to verify how all of these journals and web sites conduct text searches makes it impossible to draw any conclusions from these numbers, but it does seem that compared to at least some other fields, theoretical linguistics uses the word "crucially" more often. (I'm for the most part leaving aside the issue of whether every article uses "crucially" in the sense I'm talking about; however, I did hand-check a number of the articles, which did indeed use it in the argumental sense I described above. Additionally, "crucially" is fairly rare in standard language, as evidenced by the COCA search.) The PI numbers I believe are ridiculously inflated; it looks like the results I got were for any issue of the journal that contained the word "crucially", rather than searching within the individual articles.