Sylvain Bromberger, emeritus, works in two areas: the philosophy of linguistics, and what he calls the "theory of ignorance." His research in the philosophy of linguistics, carried out in part with Professor Morris Halle of the linguistics section, includes research on the foundations of phonology and of morphology (see e.g. "Why Phonology is Different," Linguistic Inquiry, 20 or "The Ontology of Phonology" reprinted in Essays On What We Know We Don't Know). He is thus interested in the philosophy of science as it applies to aspects of the study of language that philosophers have tended to neglect. His work on "the theory of ignorance" focusses on the selection of questions in rational inquiry. What values and what constraints bear on such selections? This has led him to work on the nature of explanation, of theory, of natural kinds, etc. Essays On What We Know We Don't Know, a collection of some of his papers on these matters, was published jointly by the University of Chicago Press and CSLI at Stanford (1992).