The Status of that in Relative Clauses
So far, we have been taking for granted that that within a relative clause is a relative pronoun, acting as a variant of who and which.
Examples:
1. The spy who / that came from the cold.
2. The golden gun which / that was made prominent by 007.
But can this assumption be upheld? That on the one hand, and which and who(m) on the other have some differences after all: that can only be used at the beginning of relative clauses- whereas who/which can occur after prepositions.
Examples: The words within the brackets are relative clauses. And obviously that is only practicable as the introducing first word of a relative clause.
1. the box [that the children keep their toys in]
2. the guy [that he handed over to the police]
3. the box [in which the children keep their toys]
4. the guy [whom he handed over to the police]
5. the box [in that the children keep their toys] wrong!
6. the guy [to that he handed over to the police] wrong!
Also, there exists no standard possessive form of that, contrasting the wh-relative pronouns who and which, which have the possessive counterpart whose. (“The box that’s the children keep their toys in”, or “The guy that’s he handed over to the police” don’t constitute grammatical English sentences). A further point to regard is the difference between restrictive and nonrestrictive relative clauses: that only applies to the former! Starting with restrictive clauses, mind that they, other than nonrestrictive relative clauses, have no “comma pause” between the head NP and the relative clause!
Examples:
Restrictive relative clause:
The fat kid [who Chleb knows] didn’t show up at school today.
Nonrestrictive relative clause:
Teacher Dickinson, [who Chleb knows], did show up at school today.
In the restrictive relative clause that can replace the who. But this is not possible in the nonrestrictive relative clause:
Restrictive relative clause:
The fat kid that Chleb knows didn’t show up at school today.
Nonrestrictive relative clause:
* Teacher Dickinson, that Chleb knows, did show up at school today.
There are two ways of explaining the witnessed differences:
- The first approach simply states that that cannot function as object of a preposition, as a possessive, or in nonrestrictive relative clauses.
- The second approach would state that the that used in relative clauses simply is not a relative pronoun. It rather is the complementizer that, which functions as a marker of an embedded sentence (as in Alex thinks that Pat is a good doctor.).
The second approach explains why the relative clause that only appears at the beginning of sentences, this being the nature of complementizers. The approach also explains why that cannot function as object of a preposition or possessively, because a complementizer simply is not a NP- and they’re the only ones that occur in those ways.
The second approach emphasizes the parallel between that relatives and bare relatives. Just as declarative complement clauses can be with or without that (Alex thinks (that?) Pat is a good doctor), so can restrictive relative clauses. So, every bare relative can alternatively be expressed as a that relative.
(Note that the opposite does not hold: if the relativized element is the subject of the relative clause that is obligatorily required.)
The advantage of this second way of explanation is that with these properties of that it may be distinguished from who(m)/which inevitably and by its very nature.
So, even though the idea that relative that is a complementizer seems unintuitive at first sight, there are many arguments in favor of it.