Movement to Spec IP(60) vP
DP v'
they v VP
e IP V'
- I' V
I vP think
will Larry leave
(61) a *they think 1 -e [VP [IP - will Larry leave] t 1 ]
b they think 1 -e [VP [IP Larry 2 will t 2 leave] t 1 ]
The word order within the embedded clause shows that the subject does not get
Case in its original position and that like any other subject, it has to move to get Case
in the subject position of the IP. Considering where a light verb can assign Case to, i.e.
the specifier of its own VP complement, and where it cannot assign Case to, i.e. the
specifier of a VP inside another clause, it is obvious that there is some locality
restriction on Case assignment in addition to the directional one. We are not yet in a
position to be able to determine the exact nature of this locality condition and so for
now we will just assume that a light verb can only Case mark elements within its own
clause.
Having put this in place, we can see that the subject will not be able to be case
marked in its original position as it is on the wrong side of the local light verb and too
far from any other light verb that might have a Case to assign.
Let us now turn to the landing site of the movement. The subject moves to a
position to the left of a modal and so the obvious place to assume as its landing site is
the specifier of IP:
(62) IP
DP 1 I'
I vP
will t 1
This must be a Case position as the sentence is grammatical with the subject sitting in
it and therefore the Case Filter must be satisfied. If we assume that it is the inflection
which is responsible for assigning the Case we account for why this is the landing site
for this movement. Moreover, we also account for the difference between the subjects
of finite and infinite clauses. Recall that while the subject of the finite clause has
nominative Case, the typical Case for the subject of the non-finite clause is accusative: