Theory, data, and the epistemology of syntax

Syntactic theory has tended to vacillate between implausible methodological extremes. Some linguists hold that our theories are accountable solely for the corpus of attested utterances; others assume our subject matter is unobservable intuitive feelings about sentences. Both extremes should be rejected. The subject matter of syntax is neither past utterance production nor the functioning of inaccessible mental machinery; it is normative — a system of tacitly grasped constraints defining correctness of structure. There are interesting parallels between syntactic and moral systems, modulo the key difference that linguistic systems are diverse whereas morality is universal. The appropriate epistemology for justifying formulations of normative systems is familiar in philosophy: it is known as the method of reflective equilibrium.