"Give him a box that everyone knows what it contains."

Is this correct English? It sounds wrong to me.

2 Answers 2


Congratulations, @Eric, you've just rediscovered one of the Ross Constraints.
These are constraints on syntactic rules of certain kinds that were discovered
by Haj Ross, in his 1967 MIT dissertation Constraints on Variables in Syntax.

With the sentence you provide

  • Give him [a boxᵢ [that everyone knows [what itᵢ contains]]]

There are three nested clauses. One, Give him a box, is the main clause.
There are two relative clauses, one modifying the other:

  • the free relative (or embedded question) what it contains, from the things that it contains.
    The things that it contains, in turn, is the direct object of the verb knows in
  • the relative clause that everybody knows what it contains,
    which modifies the noun phrase a box, the direct object of the main clause.

The problem is that, according to the rules of relative clause formation, that it shouldn't be there. Suppose the sentence was

  • *Give him a book that everybody has read it.

That sentence is ungrammatical (that's what the asterisk means).
If you're a native English speaker, you can tell by the feeling you get.
The relative clause rules should move it to the front, and change it to which, or that, producing

  • Give him a book that/which everybody has read.

which is normal. But that didn't happen in the original sentence.
To see why, compare the original sentence with and without the it

  • *Give him a box that everyone knows what it contains.
  • *Give him a box that everyone knows what contains.

Neither one is terrific, but the second one is just godawful,
while the first one, by comparison, seems only mildly off.

What Ross discovered was that there were constructions, which he called "islands" -- headless relative clauses are one kind -- which set up boundaries to movement rules like the movement part of relative clause formation.

In other words, that it can't just be yanked out and moved to a position after box,
because it's inside a headless relative, which is an island and whose contents are therefore protected against extraction rules.

This post goes into more detail about syntactic islands; Part 5, at the end,
explains why this kind of sentence occurs, using a different example pair:

  • *That's the book that Bill married the woman who illustrated it.
  • *That's the book that Bill married the woman who illustrated.
  • 4
    It's not grammatical and there's no way to make it grammatical except by starting over and avoiding the island construction. That's the point. As it says in the link: "Violations of Ross Constraints are very ungrammatical. Most people never encounter them. We appear to formulate our discourse to avoid them. Occasionally, we get in a bind and see one looming at the end of the clause, and have to do something quick." So we use a resumptive it, which doesn't make it grammatical, but avoids the Ross constraint trainwreck. Commented May 29, 2014 at 13:55
  • 1
    And why not Give him a box whose contents are known to everyone?
    – WS2
    Commented Jul 20, 2015 at 20:58
  • 2
    Nothing's wrong with them. That's why they're grammatical. They avoid the island construction by nominalization. Commented Jul 20, 2015 at 21:38
  • 2
    “Neither one is terrific, but the second one is just godawful, while the first one, by comparison, seems only mildly off.” — I find this somewhat surprising, because it's exactly backwards to me. Neither is terrific, I agree; but whereas the second is just clumsy and inelegant, the first is completely and utterly monstrous, nonsensical, and ungrammatical to me. (It's times like this when English could really use a good donc like the French. Problem solved!) Commented Jul 20, 2015 at 21:42
  • 1
    @Jacinto Yes, dont, not donc. Brain fart on my part. Commented Mar 23, 2017 at 18:50

"Give him a box" and "everyone knows what it contains" are both fine as independent units. The problem is with the attempt to splice them together with that. This is because everyone knows what it contains ought to be a dependent clause, but is constructed like a main clause.

The solution is to reword the second element so that it becomes a true dependent clause. For instance:

"Give him a box whose contents everyone knows."

"Give him a box which everyone knows the contents of."

  • 1
    A more direct, though also clumsier, option is to simply delete the extra subject in the dependent clause: “Give him a box that everyone knows what contains”. It should also be noted that (perhaps only recently?) sentences like the one in the question are, or have become, extremely common in colloquial speech, at least in AmE. Same with the ‘dangling which’, as in “I’ve always loved Pacman, which, I don’t know if you know what that is, but …”. I think it’s relatively recent, ’cause it still jars and bugs me. Sooner or later, I’ll probably stop noticing and even start doing it myself. Commented May 28, 2014 at 22:50
  • 1
    @JanusBahsJacquet - “Give him a box that everyone knows what contains” is barbarous to my ears, though understandable. That being said, I think many horrible constructions are inevitable by-products of the fact that in speech, most people are extemporizing most of the time and are also prone to getting distracted, losing their train of thought, or being thrown off course by interruptions. So, particularly when they are speaking rather than writing, we ought to be willing to cut other people some slack (and should expect to be given some leeway ourselves).
    – Erik Kowal
    Commented May 29, 2014 at 4:53
  • Changing the structure of the last relative a bit to a predicative sentence reduces the barbarosity entirely, though: “Give him a present that everyone knows what is” is fine, while a version with ‘it’ is still monstrous. Incidentally, I find the original sentence with ‘it’ far more jarring than the one without. “… that everyone knows what contains” is clumsy but grammatical to me, while “… that everyone knows what it contains” is clumsy, illogical, and utterly ungrammatical to my ear. Commented May 29, 2014 at 6:59
  • 2
    "Give him a box whose contents are known by all" Commented Mar 23, 2017 at 17:08

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