page_title: PRO (linguistics)
section_title: Nominal agreement
hierarchical_section_title: PRO (linguistics) / Motivation for PRO / Nominal agreement
caption_attribution_description: English: This is a syntactic tree diagram of the sentence "They want their son to become a millionaire" in order to show the relation between PRO ('big pro') and an overt subject with regards to noun plurality.
context_page_description: In generative linguistics, PRO is a pronominal determiner phrase without phonological content. As such, it is part of the set of empty categories. The null pronoun PRO is postulated in the subject position of non-finite clauses. One property of PRO is that, when it occurs in a non-finite complement clause, it can be bound by the main clause subject or the main clause object. The presence of PRO in non-finite clauses lacking overt subjects allows a principled solution for problems relating to Binding Theory.
  Within Government and Binding theory, the existence and distribution of PRO followed from the PRO Theorem, which states that PRO may not be governed. More recent analyses have abandoned the PRO Theorem. Instead, PRO is taken to be in complementary distribution with overt subjects because it is the only item that is able to carry null case which is checked for by non-finite Tense Markers, for example the English to in control infinitives.
context_section_description: Evidence that non-finite clauses have a phonologically null PRO subject comes from the fact that predicate nominals must agree with the subject of a copular clause. This is illustrated in (5) and (6). Example (5) shows that the number of the predicate nominal must agree with that of the overt subject: in (5a) the singular subject (their son) requires a singular nominal predicate (millionaire); in (5b), the plural subject (his sons) requires a plural nominal predicate (millionaires). The examples in (6) show that the same contrast holds of PRO subjects: if PRO is controlled by a singular antecedent, in (6a) the subject of want, then the predicate nominal must be singular; if PRO is controlled by a plural antecedent, as in (6b), then the predicate nominal must be plural.
  The following tree diagrams show how PRO, as the subject of the copular clause, enters into agreement with the nominal predicate introduced by the copular verb become. The application of agreement is automatically explained if PRO is co-indexed with the subject of the main clause, with the predicate nominal simply agreeing with the number features of the argument that controls PRO, just as it would be if an overt subject had been introduced.
caption: Tree Diagram for (5a)
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