Structureachieve nothing and we would be better off not adding it and keeping things simpler.
Moreover, why would we want to make the grammar explain facts that had nothing to
do with it: it would be like trying to get the laws of gravity to explain why red balls
fall to the ground at the same speed as blue ones do.
Let us therefore assume the grammar to contain a rule which informally might be
stated as follows:
(5) a sentence can be made up of (at least) words and sentences
This rule defines sentences in terms of sentences and so the definition refers to what is
being defined. A rule that does this is known as recursive, and recursive rules have
exactly the property that we want to be able to define human languages. Recall from the
discussion in Chapter 1, human languages are limitless and yet they must be defined
by a finite set of rules as the human head can only store a finite amount of information.
If I-languages are made up of recursive rules, then a finite set of these will be capable
of defining an infinite number of expressions that make up an E-language.
The rule in (5) can be stated a little more formally in the following way:
(6) sentence Æ word, sentence
This rule introduces a number of symbols to replace words used in (5). The point of
this is to make properties of the rules more obvious. Recall that generative linguists
insist on making their grammars explicit so that we are able to test and question the
assumptions being made and it is easier to see properties of rules when stated as a
formula than it is if they are given as a set of linguistic instructions, especially as the
rules become more complex.
We can read the rule in (6) as follows. The arrow indicates that the element on the
left (sentence) is defined as being made up of the elements on the right (word,
sentence). The asterisk after word and sentence indicates there can be any number of
these elements. Thus the rule states that a sentence can be made up of a sequence of
words and a sequence of sentences.
At the moment, this is not a particularly accurate rule as it is not the case that
English sentences are simply made up of sequences of words and sentences without
further restrictions. We have introduced it purely for expository purposes. To make
things more accurate we need to introduce another concept.
1.2 Phrases
We have said that a sentence can consist of a predicate and its arguments. So in a
sentence such as (7):
(7) Prudence pestered Dennis
we have the verb pestered as the predicate which relates the two arguments Prudence,
the agent and Dennis, the patient. Now consider a slightly more complex case:
(8) the postwoman pestered the doctor
This could mean exactly the same thing as (7), on the assumption that Prudence is a
postwoman and Dennis is a doctor. In this case the arguments seem to be the
postwoman and the doctor, a sequence of words made up of a determiner followed by