While the discussion on theta roles seems tangential, it allows us important leeway. We can now break sentences up, by constituents into a subject, a verb and an object. As well, dividing arguments into internal and external arguments provides a syntactic difference between objects and subjects: objects are verb internal, subjects are external.
This leaves with the tentative sentence structure rule:
S–> NP + VP
The variation in object presence can now be explained by a variation in the subcategorization of the verb: each sentence entails a complete thought, and thus requires all the elements of an event.
Looking at our prior phrase structure rules, it is clear that some things are missing. While I could give the relevant example sentences in post after post, redefining the rules again and again, I will skip to a relatively finished product, and just list the changes (and examples for each phrase rule).
1. adjectives and prepositional phrases can be a part of noun phrases
2. Adjectives are phrasal elements
S –> NP – VP
NP –> (Det) – (AP) – N – (PP)
a brown puppy
The Duke of Earl
VP –> V – (NP) – (PP)
put the microwave in the toilet
devoured the cake
slept in his bed
PP –> P – NP
in his bed
AP –> A – (PP)
sick of fish
How could this system be modified to deal with the following sentences?
(23a) The student of physics with long hair
(23b) Sven put the microwave in the toilet on Friday
(23c) The doctor was killed with the golf club by the butler with a limp at 12 o’clock on Friday in the Atrium
The problem is as follows: both sentences are grammatical sentences of English, yet cannot be generated by our current set of rules. (23c) may be a bit awkward, but moving the prepositional phrases around can create more palatable orders, and is in there for the purpose of highlighting the issue.