It was once thought that pronouns are nothing more than the product of syntactic laziness. Their role, it was suggested, is merely to obviate the need, and tedium, of repeated occurrences of structurally identical noun phrases: where a sentence contains an occurrence of a pronoun, it functions as a replacement for an occurrence of a noun phrase displayed elsewhere in the sentence (or perhaps in the context). Although this view was later modified to include the caveat that pronoun-substitution (pronominalization) could occur only where the noun phrases concerned are co-referential, the thesis remained essentially syntactic; that is, pronouns were seen to originate as proxies for identifiable syntactic units.