Problem 8.3 All of the constraints are necessary. None follows from the others.
- Structural licensing refers to a different property of the formalism
than matching or biuniqueness and so cannot be derived from them nor they
from it. Structural licensing defines the phrase structure configuration
in which case licensing occurs, while biuniqueness refers to the number
of cases that a head can check and matching refers to which particular cases
a head can check.
- Biuniqueness and matching are clearly independent of each other as well.
Without biuniqueness, two different arguments of a single head could be checked
by a single Case feature of that head. Without matching, the actual values of Case
features would be irrelevant, since there would be no mechanism to distinguish
different Case features from each other.
- Exocentricity is needed to keep a determiner from assigning case
to its own DP maximal projection. Without exocentricity, DP's could
appear where no external case assigner was present, for example as
the subject of any infinitive. None of the other constraints prevent
this. Exocentricity can be thought of as a structural licensing condition, but
it is not reduceable to the condition in (43).
Biuniqueness cannot be derived from structural licensing and exocentricity
combined because the addition of the latter to the former doesn't affect the
relevant cases, For example, without biuniqueness a verb, head of VP,
could license accusative case on both its specifier and its complement, under
the Head-Spec and Head-Complement configurations, respectively. Then DP's could
appear freely as subjects of non-finite transitive verbs.