Raising and Controlreferential properties, as it does not appear to behave like other pronouns in this
respect. We will consider these points separately.
PRO can be found in the subject position of non-finite clauses:
(66) a we attempted [PRO to work the machine]
b they tried [PRO turning the wheel]
c I painted the ceiling [PRO balanced on a chair]
It does not ever appear in the subject position of a finite clause, the object position or
the object of a preposition:
(67) a the message said [that PRO would self-destruct in five seconds]
b I congratulated PRO
c *the guard spoke to PRO
Note that there is nothing semantically wrong with these sentences. As PRO is a
pronoun that refers to some other element in the sentence, the meaning of the
sentences in (67), were they grammatical, would be perfectly understandable:
(68) a the message said [that it would self-destruct in five seconds]
b I congratulated myself
c the guard spoke to himself
Why is it that PRO cannot appear in these positions? One relevant observation is
that these positions are those to which Case is assigned. The non-finite subject
positions, in which PRO is allowed, seem to be Caseless as overt DPs cannot appear
there and so presumably they violate the Case Filter:
(69) a we attempted [Sid to work the machine]
b they tried [Tony turning the wheel]
c *I painted the ceiling [Bob balanced on a chair]
If PRO must avoid Case positions, we predict that we should not be able to go in the
subject position of the non-finite complement of a exceptional verb, as this is a
position assigned Case by the light verb of the exceptional verb. This expectation is
indeed fulfilled:
(70) a he believes [PRO to be rich]
b I suppose [PRO to drive a Trabant]
Similarly, PRO will not be able to appear with a for complementiser, which we have
argued assigns Case to the subject position of the non-finite clause that it introduces:
(71) a she hoped [for PRO to be on TV.]
b we were anxious [for PRO not to be late]
In such cases, if the complementiser is absent, the sentence is grammatical:
(72) a she hoped [PRO to be on TV.]
b we were anxious [PRO not to be late]
So it seems that PRO cannot appear in Case positions and is therefore in
complementary distribution with overt DPs, which of course must sit in Case positions.