filter (n./v.)

A process first recognized in the STANDARD THEORY of GENERATIVE GRAMMAR, whereby in a DERIVATION only certain BASE PHRASE-MARKERS are transformed into SURFACE STRUCTURES, others being ‘filtered out’ by the application of various CONSTRAINTS (specified, for example, by the non-lexical TRANSFORMATIONS). It assumes a more central role in GOVERNMENT-BINDING THEORY, where it refers to a type of CONDITION which prevents the generation of UNGRAMMATICAL SENTENCES. Filters state simply that any structure of type X is ILL FORMED. They are also known as ‘OUTPUT constraints’ or ‘surface-structure constraints’. For example, a ‘FOR–FOR filter’ has been proposed, which states that any surface structure containing the sequence for–for is ungrammatical; this thereby excludes the generation of sentences in which VERBS like hope for are used along with their for+INFINITIVE COMPLEMENTS (cf. What she is hoping for is for John to win), as in the ungrammatical *She is hoping for for John to win.

It is important to distinguish ‘filters’ from ‘constraints’: the former apply solely to the structure which is the output of a given set of RULES; the latter apply to two successive stages within a derivation. Filters are claimed to be more general, more UNIVERSAL and more constraining on theory construction than the constraints which restrict the application of specific rules: a filter BLOCKS the generation of a sentence (S), regardless of the set of rules which have applied in generating that sentence, whereas a constraint blocks the application of a specific set of rules to produce S (thus allowing the possibility that S might none the less be generated by the application of other sets of rules).