best-known for her work on systems of modal logic. Marcus gained her PhD at Yale in 1946, and subsequently held posts at Illinois-Chicago and Northwestern before becoming Halleck professor at Yale. Her seminal papers showed how formal languages could consistently combine names and quantificational structure with modal operators, contrary to the prevailing negative opinion energetically voiced by Quine. Marcus also made significant contributions to deontic logic. A doughty champion of analytic rigour, Marcus was a formidable opponent of continental and literary tendencies in Anglo-American philosophy. Her papers are collected in Modalities: Philosophical Essays (1993). See also modal logic; Barcan formula; identity, necessity of.