English philosopher and educator noted for his study of the history of ideas. He was concerned with describing prescriptive language—that is, imperative sentences and value judgments used for ethical statements—while holding that ethics, or the logical study of moral language, cannot be reduced to subjective or objective facts but is a unique expression of duty or right.

Educated at Cambridge University (D.Phil. in philosophy, 1948), he lectured at Oxford before becoming department head and professor at the University of Leeds (1955–59) and then director of the Nuffield Foundation (1960–64). Moving to the United States, Toulmin taught at Brandeis University (1965–69), Michigan State University (1969–72), the University of California, Santa Cruz (1972–73), the University of Chicago (1973–86), and Northwestern University, Evanston, Ill. He was the author or coauthor of An Examination of the Place of Reason in Ethics (1950), The Ancestry of Science, vol. I, The Fabrics of the Heavens (1961), vol. II, The Architecture of Matter (1962), and vol. III, The Discovery of Time (1965), Human Understanding (1972), Knowing and Acting (1976), An Introduction to Reasoning (1979), and The Return of Cosmology (1982).