First of all, this is not a duplicate… E.g., have a look at these posts:
"as … as" or "so … as" for comparison?
Anytime people on those posts talked about the use of 'so…as…', they said either that it can be used 'only in negative context' or that it can be used 'only with negative comparatives'.
Well, it is not clear to me at all what is meant by 'negative context/comparatives'… I am quite sure there was something significant omitted in the explanations. E.g., look at the following sentences:
Like the coordinating conjunctions, it is perfectly fine to begin sentences with because, so long as you keep in mind that the goal is to avoid fragments.
(Source: https://ell.stackexchange.com/a/564/6697).
This sentence does not seem to contain any 'negative context/comparatives'.
So foolish, unreasonable, or out of place as to be amusing.
(Source: the definition of 'ludicrous' on Oxford Dictionaries).
This sentence does not seem to contain any 'negative context/comparatives' either.
And this post was not meant to be derogative in any way… I am sorry if anyone got offended.
I have also left the exact URLs of most of the websites I have linked to (without having used the hyperlink function) so as to let the users see some information about the links given before having them clicked on the link.
(additionally, is 'before having them clicked on the link' grammatical? I am not a native English speaker and I'm trying to get a hang of some more advanced kind of structures).
Some justifications of the uses of 'so…as…' in the two given sentences would be appreciated (as well as some other grammar corrections present in this post, if possible). Thanks!
Best Answer
The posts you link to speak of the use of so ... as ... and as ... as ... in comparisons. In that context the “rule” is as stated: so is employed only in negative comparisons.
But in the two counterexamples you cite, there is no comparison. It is not asserted that the measure of one quantity or degree is less than, greater than or equal to the measure of another. Rather
In the first, the so... as ... construction is used not relatively but absolutely, to introduce a measure of the extent to which the preceding assertion is true. There is only one measure, not two.
While expressions of this sort undoubtedly have the same origin as the comparative construction, the difference between the two uses is so marked that they are no longer apprehended as the same. In the early 20th century so was deprecated in this use, but it has always alternated freely with as in ordinary speech, and today it is generally permitted again.
In the second the construction is not so ... as ... but so ... as to VERB, with the same sense as so ... that it VERBs: “so foolish ... that it is amusing”. Again, this is not a comparison of two measures but a single measure.