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Much of (what/which) scientists know about dinosaurs has been recently discovered.

The phenomenon of (what/which) are known as corporate networks has also attracted attention.

And yes, the answer is what. But why?

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It may be a duplicate question, but the "possible duplicate" answer doesn't explain why; it just lays down the law. And there is an answer, but it's complicated, so this will probably get closed before it gets answered. – John Lawler Jul 3 '12 at 13:34
up vote 6 down vote accepted

Both of the clauses beginning with what are noun clauses. You can tell they're noun clauses because they're both the object of the preposition of.

  • much of [what scientists know about dinosaurs]
  • the phenomenon of [what are known as corporate networks]

Noun or complement clauses can function like nouns -- as subject, direct object, or prepositional object.

There are four types of complement clauses in English, and this is the type called an Embedded Question complement. (the others are Infinitive, Gerund, and tensed That-clause.)

Embedded questions are just regular Wh-questions, but they have three peculiarities that mark them as subordinate clauses:

  1. Embedded Yes/No questions use whether (whether only occurs in embedded questions)
  2. Embedded questions do not invert Subject and Verb.
  3. Embedded questions do not use which, but rather what.

It's the third peculiarity that's responsible; the normal distinction between open what and closed which is simply not available in embedded questions, just like the usual future sense of will is unavailable in if-clauses. There's a reason.

Which already has a role as a relative pronoun (and you can't use what as a relative pronoun). Relative pronouns are Adjective clauses, while Embedded Questions are Noun clauses. The purpose of an introductory marker like what or that or which is to indicate -- before it's parsed -- what kind of clause is coming up.

If which already marks adjective clauses, it's confusing to have another which that marks noun clauses. So we don't. What marks noun clauses and which doesn't, while which marks adjective clauses and what doesn't. That's all, really. It's kind of like opposing metal to colour in heraldry -- it improves clarity and avoids confusion in the signal.

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"Much of what was left" is different to "much of which was left" because the first describes a thing, and the second describes an action. Does that fit into what you've described above? – Matt E. Эллен Jul 3 '12 at 14:25
The first clause is a headless relative, meaning "that which was left"; since the antecedent of the relative is missing, it's effectively a noun clause, and that's why what introduces headless relatives. The second clause has a normal relative which, but there is a pied-piped NP and preposition in front of it. – John Lawler Jul 3 '12 at 14:41
I see! Thank you. – Matt E. Эллен Jul 3 '12 at 14:45
Addendum; today I listened again to the late Andy Griffith's "What it Was, Was Football" story, and noticed that he uses a that after before in the clause "before that we set up the tent," and maybe elsewhere as well. His accent is very rural North Carolina, but accurate, though a bit exaggerated to match the naivete of the character. – John Lawler Jul 3 '12 at 19:58

One difference between the usage of "What" and "Which" is the difference between Noun Clauses and Adjective (Relative) Clauses.

The same confusion occurs when a student makes a sentence like:

The information WHAT scientists know about dinosaurs is limited. = X

This sentence should be:

WHAT scientists know about dinosaurs is limited. = Noun Clause


The information THAT scientists know about dinosaurs is limited. = Adjective Clause

Similarly, "Which" will become possible in your sentence inside an Adjective Clause. For example,

There is an existing body of knowledge about dinosaurs, much of WHICH has recently been discovered.

People are flocking to build what are known as corporate networks, the phenomenon of WHICH has attracted a lot of attention.

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This isn't really a difficult one, watch this:

Question: What do you know about dinosaurs?

Make it to:

Question: What do scientists know about dinosaurs?

Answer with:

Most of what scientists know about dinosaurs has been recently discovered.

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The difference is that which is a relative pronoun and requires an antecedent, whereas what is not (at least in all Standard Englishes that I am aware of).

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'Which' is also a question where there is choice or selection from a finite number of things. 'Which one do you like, the green one, the red one or the blue one? – Barry Brown Jul 4 '12 at 7:57
True, but how is that relevant to the question? – Colin Fine Jul 4 '12 at 21:44

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