Theoretical Aspects of MovementThe three X-bar rules introduce three elements besides the head. The complement
is introduced as the sister of the head. It always follows the head and is restricted by
the head’s subcategorisation requirements. Thus, if a head selects for a PP
complement, the complement must be a PP. The specifier is introduced as the sister to
X' and daughter of XP. Specifiers precede the head and are restricted to one per
phrase. The last element of the phrase, the adjunct, can be introduced at any X-bar
level: X, X' and XP. This element expands what it is adjoined to into another element
of the same type. Therefore the process is recursive and in principle any number of
adjuncts can be added to a structure.
We will have far more to say about X-bar structures as we proceed through this
book and many more examples of heads, complements, specifiers and adjuncts will be
provided. However, all of these will conform to the basic principles set out here and as
such the theory of structure provided by X-bar principles is an extremely general and
explanatory one.
2 Theoretical Aspects of Movement
Consider a sentence such as the following:
(46) who does Harry hate?
The verb hate typically has two arguments, experiencer and theme, and is transitive
with the theme as its object:
(47) Harry hates him
But in (46) the object appears to be missing. This is not a case of an ‘understood’
object, where the argument is present at a semantic level, as it is fairly obvious that the
interrogative pronoun who has the grammatical function of the object. Yet, this
pronoun is not sitting in the canonical object position, the complement of the verb,
directly after it. Indeed, the interrogative pronoun is occupying a position that no other
object can occupy:
(48) *him does Harry hate
The obvious questions to ask are: why is the object sitting at the front of the
sentence in (46)?; and how is the interrogative pronoun interpreted as an object when it
is not sitting in an object position? As to the first question the obvious answer is that it
has something to do with the interrogative nature of the clause: the clause is a question
and interrogative clauses of this kind start with an interrogative phrase such as who.
The second question is a little more difficult to answer. In English, an element
typically is interpreted as object depending on the position it occupies:
(49) a Harry hates him
b He hates Harry
In (49a), the pronoun him is interpreted as the object as it is sitting in the complement
position. Harry on the other hand is the subject and is sitting in a specifier position. In
(49b) it is the other way round: He is the subject, sitting in the specifier position, and
Harry is the object, sitting in the complement position. If who in (46) is interpreted as