Why do not we ask negative questions without a contraction on the not after the verb?
This is an interesting question. I haven't an authoritative answer, but I can sketch the historical development and make some suggestions for how it came to be.
The first thing is that not is an anomaly in English: it is a kind of modifier that follows the word it modifies. This is normal in some languages, but unusual in English, where modifiers (such as adjectives and quantifiers) usually precede.
Historical forms like
I go not
with not post-modifying go actually arose from older I ne go nought (Old English, but with modern spelling for simplicity) where nought was optionally used for emphasis, and gradually became compulsory and ne disappeared. An exactly similar process can be seen in French Je ne sais pas. ("I don't know"), where the originally empatic pas is now normally required, and in everyday speech the ne pretty well disappears. This cross-linguistic process is known as Jespersen's cycle.
So in early modern English, the anomalous I go not was the norm.
The optional use of do with a verb goes back at least to Shakespeare's day: I do go is grammatical now as it was then (though today it has a special meaning, either I go habitually, or a contrastive or emphatic sense). This meant that in the negative I do not go was available as an alternative to I go not.
For some reason this form ousted the older form except for auxiliaries: we still say I will not, I cannot etc., but for full verbs, only He does not see it is available. My own theory is that the "do" form gained ground precisely because it restores the usual modifier-modified order: I do not go can be seen as having the pre-modifer do not before the main verb go. When the contraction don't is used, this is even stronger. But I've not seen this idea discussed anywhere.
In negative questions there is a further complication. The early modern English form was
Go they not?
which appears frequently in the King James Bible.
With the rise of do support in the negative (and interrogative), it appears too in the negative interrogative:
Do not they go?
and as A E says, this was still common in 1800, as can be seen in Jane Austen and other writers.
But there was another form which also appeared, I believe from a reanalysis of They do not go as They do (not go) rather than They (do not) go: when this was inverted as a question, the simple auxiliary do was inverted with the subject, and the not go stayed together, giving Do they not go?
When do not was contracted to the single word don't, on the other hand, this reanalysis was not possible, and the compound don't was what inverted with the subject, giving Don't they go?
As I said, this is a descriptive account, not really an explanatory one. But I suspect it is the best answer available.
There are several rules involved here.
Not-Placement, which puts not immediately after the first auxiliary verb.
Auxiliary-Negative Contraction, which optionally produces a single contracted auxiliary.
Question Formation, which inverts the subject and the first auxiliary verb.
These first three rules all require an auxiliary verb.
If there is none, one more rule gets involved:
-
Do-Support, the rule that supplies the auxiliary do to use with these rules.
(Auxiliary do carries the tense, so the main verb is changed to an infinitive)
In modern English Do-Support is obligatory; i.e, we can't ask questions like
- *Slept you 8 hours yesterday?
any more.
Furthermore, Auxiliary-Negative Contraction produces a single contracted auxiliary.
And it does so optionally; this means one can form a question either with or without contraction.
So let's form questions both ways and see what happens.
You slept 8 hours yesterday. (Base sentence)
Here's negative question without contraction:
You did not sleep 8 hours yesterday. (Not goes after Do-Support did)
Did you not sleep 8 hours yesterday? (Auxiliary did inverts with subject you; not stays put)
Here's negative question with contraction:
You did not sleep 8 hours yesterday. (Not goes after Do-Support did)
You didn't sleep 8 hours yesterday. (Contracted auxiliary formed)
Didn't you sleep 8 hours yesterday? (Contracted auxiliary inverts with subject you)
As you can see, the question rule is quite specific. The first single auxiliary verb can invert, and contracted auxiliaries are single auxiliary verbs. And there's no other rule to move the uncontracted negative along with the auxiliary. After all, until it's contracted, not is just another adverb.
In general, once a word has been reified, it's a different word, with different affordances.
- Don't you sleep?
- Do you not sleep?
- *Do not you sleep? (weird)
Whilst it's a good question, the assumption in the Original Poster's discussion is kind of the wrong way round. It is not the case that "not" must contract when it appears directly after the auxiliary verb. What's happening is that, to make the sentence into a question, the auxiliary is moved to the front of the sentence from its normal position:
- You do sleep.
- Do you sleep.
Not can only move from its normal position if it's stuck to this auxiliary verb. It's the auxiliary that's carrying not round to the front of the sentence. It can only do this if they're joined together.
If not isn't contracted, it must stay in the same position it has in a normal declarative sentence. Below the parts that invert are in light font, the rest of the sentence is in bold. In sentence (3) we see not moved away from it's normal position because it's attached to the auxiliary verb. It's sandwiched between the auxiliary and the subject:
- Tom does not like Sally (normal negative sentence)
- Does Tom not like Sally (no contraction, not in normal declarative sentence position)
- Doesn't Tom like Sally (contracted with auxiliary, n't appears in pre-subject position)