Lewis, C. I.

Lewis, C. I. (Clarence Irving) (1883–1964) philosopher; born in Stoneham, Mass. Directed to social problems by his father, a shoemaker blacklisted for union activities, and encouraged in philosophy by an elderly woman he met during a summer job, he graduated from Harvard in 1905, having studied under William James and Josiah Royce. After earning a Ph.D. (1910) he taught at the University of California: Berkeley (1911–20) and Harvard (1920–53). He developed a logic of strict implication, a pragmatic theory of knowledge, and a naturalistic value theory; his works include An Analysis of Knowledge and Valuation (1946).