X-bar Theory(19) XP
YP X'
V YP
fall
These features then project to the X':
(20) XP
YP V'
V YP
fall
And finally they end up on the maximal projection:
(21) VP
YP V'
V YP
fall
In this way we can see that categorial features are actually projected into structures
from the lexicon. This makes a lot of sense given that categorial properties are to a
large extent idiosyncratic to the words involved in an expression and are not easily
predicted without knowing what words a sentence is constructed from. Things which
are predictable, such as that all phrases have heads which may be flanked by a
specifier to its left and a complement to its right, are what are expressed by the X-bar
rules. Thus we have a major split between idiosyncratic properties, which rightly
belong in the lexicon, and general and predictable properties which rightly belong in
the grammar.
The structure in (21) is still incomplete however and we must now consider how to
complete it. Let us concentrate firstly on the complement position. At the moment this
is expressed by the general phrase symbol YP. This tells us that only a phrasal element
can sit here, but it does not tell us what category that phrase must be. Yet, it is clear
that we cannot insert a complement of just any category into this position:
(22) a fell [PP off the shelf]
b fell [DP the cliff]
c fell [VP jumped over the cliff]
This restriction clearly does not come from the X-bar rules as these state that
complements can be of any category, which in general is absolutely true. But in
specific cases, there must be specific complements. Again it is properties of heads