Marcus Ruth Barcan (b.1921), American philosopher best known for her seminal work in philosophical logic. In 1946 she published the first systematic treatment of quantified modal logic, thereby turning aside Quine’s famous attack on the coherence of combining quantifiers with alethic operators. She later extended the first-order formalization to second order with identity (1947) and to modalized set theory (1963). Marcus’s writings in logic either inaugurated or brought to the fore many issues that have loomed large in subsequent philosophical theorizing. Of particular significance are the Barcan formula (1946), the theorem about the necessity of identity (1963), a flexible notion of extensionality (1960, 1961), and the view that ordinary proper names are contentless directly referential tags (1961). This last laid the groundwork for the theory of direct reference later advanced by Kripke, Keith Donnellan, David Kaplan, and others. No less a revolutionary in moral theory, Marcus undermined the entire structure of standard deontic logic in her paper on iterated deontic modalities (1966). She later (1980) argued against some theorists that moral dilemmas are real, and against others that moral dilemmas need neither derive from inconsistent rules nor imply moral anti-realism. In her series of papers on belief (1981, 1983, 1990), Marcus repudiates theories that identify beliefs with attitudes to linguistic or quasi-linguistic items. She argues instead that for an agent A to believe that p is for A to be disposed to behave as if p obtains (where p is a possible state of affairs). Her analysis mobilizes a conception of rational agents as seeking to maintain global coherence among the verbal and non-verbal indicators of their beliefs. During much of Marcus’s career she served as Reuben Post Halleck Professor of Philosophy at Yale University. She has also served as chair of the Board of Officers of the American Philosophical Association and president of its Central Division, president of the Association of Symbolic Logic, and president of the Institut International de Philosophie. See also BELIEF, CAUSAL THEORY OF PROPER NAMES , MODAL LOGIC , MORAL DILEMMA , PHILOSOPHY OF LANGUAGE , PHI – LOSOPHY OF LOGIC , QUIN. D.R. & W.S.-A. Marcus Aurelius (A.D. 121–80), Roman emperor (from 161) and philosopher. Author of twelve books of Meditations (Greek title, To Himself), Marcus Aurelius is principally interesting in the history of Stoic philosophy (of which he was a diligent student) for his ethical self-portrait. Except for the first book, detailing his gratitude to his family, friends, and teachers, the aphorisms are arranged in no order; many were written in camp during military campaigns. They reflect both the Old Stoa and the more eclectic views of Posidonius, with whom he holds that involvement in public affairs is a moral duty. Marcus, in accord with Stoicism, considers immortality doubtful; happiness lies in patient acceptance of the will of the panentheistic Stoic God, the material soul of a material universe. Anger, like all emotions, is forbidden the Stoic emperor: he exhorts himself to compassion for the weak and evil among his subjects. ‘Do not be turned into ‘Caesar,’ or dyed by the purple: for that happens’ (6.30). ‘It is the privilege of a human being to love even those who stumble’ (7.22). Sayings like these, rather than technical arguments, give the book its place in literary history. See also HELLENISTIC PHILOSOPHY , STO- ICIS. D.Ar.