I'll start with a simple relative clause:
the booksᵢ that he wrote ∅ᵢ are interesting
I've included a bit of theory: a
∅, signifying a gap, and subscripts that link that gap to the noun "books." That's meant to be pretty minimal theory, though, something most everyone who thinks about relative clauses can probably agree with.
The idea is that to understand this sentence, you've got to understand "the books" both as the subject of "are interesting" and as the object of "wrote"---as if it has two positions in the sentence, one in the matrix clause and one in the relative clause. Of course it's only pronounced in the matrix clause, and that's why we posit a gap in the relative clause.
Now try this one:
*the booksᵢ that she asked who wrote ∅ᵢ are interesting
As the asterisk indicates, this is supposed to be ungrammatical; anyway it's ungrammatical in my English. And in fact analogous sentences are ungrammatical in many languages.
It turns out that there are some very good generalisations about when you get failures like that: there certain configurations, which get called islands, and a gap that occurs within an island can't get linked to a position outside the island. "who wrote ∅ᵢ" is what's called a
wh island, and it's a really good generalisation that a gap inside a
wh island can't get linked to a position outside it.
One reason these generalisations are interesting is that they tend to cover not just relative clauses but also questions. So this is also bad (at least in my English):
*Whatᵢ did she ask who wrote ∅ᵢ?
That's to say, relative clauses in many languages and questions in many languages (and in fact focus constructions in many languages) are governed by a fairly unified set of island constraints, and it's reasonable to suppose that when they are, there's some particular thing that's going on that explains why they're subject to island constraints.
Now, it's not the case that all relative clauses and questions in all languages are governed by island constraints. Here's a Mandarin example:
你買了誰寫的書？
nǐ mǎile [shéi xiě ] de shūᵢ
2s buy who write DE book
"Who is the x such that you bought books that x wrote?"
(I'm taking this and other upcoming Mandarin examples from lecture notes by Michael Yoshitaka Erlewine and Hadas Kotek, available
here.)
This contains a relative clause (which I've bracketed), and relative clauses themselves are islands---but the question is fine. An obvious guess is that it's fine because the question word is
in situ, so there's nothing in the island that has to get linked with something outside of the island.
It's not so simple, though:
*他為什麼寫的書最有趣？
[tā wèishénme xiě ] de shū zuì yǒuqù
3s why write DE book most interesting
Intended: "What is the reason such that the books he wrote for that reason are most interesting?"
Here we have a relative clause island and what looks like an island effect---as if the question word
wèishénme "why" has to get linked to some position outside of the island, even though nothing is pronounced in that position.
Here's why I think that's interesting. In a case like "the books that she asked who wrote," it's pretty easy to motivate the idea that there's a gap inside the relative clause corresponding to the noun "books" outside the relative clause, and it's pretty intuitive that the issue is the relation between the gap and that noun. In the Mandarin case (the second, ungrammatical one), there's no gap inside the relative clause, but it's a bit like there's a gap
outside the relative clause, and the problem is that the question word inside the relative clause island can't get linked to the gap outside it.
In case you're thinking that the problem with that Mandarin sentence is just semantic or pragmatic, here's another good one:
他為了什麼原因寫的書最有趣？
[tā wèile shénme yuányīn xiě ] de shū zuì yǒuqù
3s for what reason write DE book most interesting
"What is the reason such that the books he wrote for that reason are most interesting?"
The semantics and pragmatics haven't really changed. Only the question word is different,
wèile shénme yuányīn "for what reason," instead of
wèishénme "why." (The Erlewine and Kotek lecture notes talk a bit about why this might be so.) So the problem with the previous example probably isn't semantic or pragmatic in nature.
It's a bit as if some Mandarin question words have to get linked in an island-sensitive way with a gap (or whatever) somewhere else in the sentence, and some do not, even though all the question words are
in situ. (And it's also not the case that sentence-initial question words always give rise to island effects, though I don't have examples to illustrate that.)
Anyway, all of that is meant to be fairly neutral between approaches to syntax. Now I'm going to sketch three very general ways you might try to account for what's going on in these cases.
First, there's the unification approach. This doesn't go much beyond what I've already said, in that it proceeds by placing constraints on what positions in a sentence can be linked in the way that's needed for some relative clause and questionn constructions. Er, I know very little about how this approach gets carried out, but my understanding is that this is how LFG and HPSG do things. (And of course once you start spelling out how the constraints are supposed to work, it'll get theory-specific pretty quickly.)
Second, there's movement. The idea here is that a sentence is put together in stages, and that one of its constituents can be in one position at one stage in the derivation, and in another stage in the derivation: it moves. So you might suppose a derivation that goes in part like this:
are you eating what
→ whatᵢ are you eating tᵢ
(This is how things are described in Government and Binding, and in G&B movement has to leave a trace; that's the
tᵢ, and it corresponds to the gap in earlier examples. A real derivation would involve more steps than that, naturally.)
Having set things up this way, you then explain island constraints with the hypothesis that you can't move something out of an island. (And you suppose that relative constructions and question constructions that don't observe island constraints don't involve movement.)
Another point worth mentioning is that nothing I've said requires that it be the last stage in the derivation that gets pronounced. If you have a language where, say, question words are
in situ but questions are still governed by island constraints, a possible analysis is that derivation of questions goes through stages just like the English example above, but it's the stage before the movement---when the question word is
in situ---rather than the stage after that gets pronounced. The result is what's called covert movement. (This is only one G&B analysis of covert movement, though.)
Third, there's whatever you have in minimalism, which is usually still called movement, but really kind of isn't. You still put sentences in stages, but it looks more like this:
are you eating what
→ whatᵢ are you eating whatᵢ
This is what Chomsky calls internal merge: something that's already been put into the sentence is inserted again, so that it occupies two positions in the sentence's structure. Some people---not Chomsky---say that it's a copy of the original that's put in the new position, not the original itself, though I don't think I've ever seen someone try to explain what copying amounts to here; and quite a lot of the time it's not obvious how you're supposed to understand what's going on here; but for Chomsky himself it's just the very same thing ending up in two positions in the structure. On no one's view does it really make sense to describe this as movement. Still, your account of island effects is a lot like the G&B one: something that's inside an island can't be re-merged into a postion outside the island.
Of course you don't say "what are you eating what"---you only pronounce "what" in one of its two positions. (Alternatively: you only pronounce one of the two copies.) In English, you pronounce it in the sentence-initial position; in an alternate
in situ English, you'd pronounce it in the other position.
(This view makes it conceivable that you could have a construction where some constituent gets pronounced more than once, at more than one position in the structure, and analyses along such lines have been made of constructions in a number of languages, including certain verb-copying constructions in Mandarin, for example.)
All that said, what about syntactic ergativity? Well, it's an intriguing fact that syntactic ergativity usually, and maybe always, constitutes a constraint on exactly the sorts of constructions where you find island constraints. This is why Chomskyans tend to describe it as a constraint on movement (A-bar movement, or extraction, in particular). But, first, I think the issue doesn't require you to believe in syntactic movement. Even evmdbm's question about English subject questions isn't necessarily about movement---you can still ask whether English subject questions require a link to be established between the question word and a gap, just like English object questions seem to. And, second, "movement" is actually a pretty bad description of what contemporary Chomskyans mostly think is going on, the fact that mostly they do and other syntacticians maybe mostly don't may bemore a cultural difference than anything at this point.
