Clarence Irving Lewis 1883-1964, American philosopher, b. Stoneham, Mass., grad. Harvard (B.A., 1906; Ph.D., 1910). After teaching (1911-20) at the Univ. of California, he was professor of philosophy at Harvard from 1920 to 1953, when he became professor emeritus. Lewis's importance as a philosopher lies in his combination of symbolic logic with an essentially pragmatic epistemology. After studying logic under Josiah Royce, he developed his own system of symbolic logic in opposition to the Principia Mathematica of Bertrand Russell and Alfred North Whitehead. However, he soon began investigations in the field of epistemology. In his main work, Mind and the World-Order (1929), he developed a position according to which the choice between logical (and thus philosophical) systems must be based on pragmatic grounds. His other works include A Survey of Symbolic Logic (1918), Symbolic Logic (with C. H. Langford, 1932), An Analysis of Knowledge and Valuation (1946), Our Social Inheritance (1957), and The Ground and Nature of the Right (1955).

Bibliography: See his Collected Papers, ed. by J. D. Goheen and J. L. Mothershead (1970); J. R. Saydah, The Ethical Theory of Clarence Irving Lewis (1969).

Clarence Irving Lewis

Clarence Irving Lewis (1883-1964), American philosopher, was a pioneer in symbolic logic and the founder of conceptual pragmatism.

Born on April 12, 1883, C. I. Lewis received his bachelor's degree from Harvard, having studied with Josiah Royce and William James. After teaching at the University of Colorado, he returned to Harvard in 1908 and was awarded his doctorate 2 years later. During this period he studied with George Santayana and Ralph Barton Perry, as well as with Royce. He had married Mabel Maxwell Graves in 1907.

In 1911 Lewis went to the University of California to teach philosophy. He was given the task of teaching symbolic logic and, finding no textbook in English for the course, set out to write one. Survey of Symbolic Logic was published in 1918 while Lewis was serving in the U.S. Army. This book contains not only the first history of the subject in English but also Lewis's own system of intensional logic based on strict implication. The final presentation of this system was Symbolic Logic (1932), written with Cooper Harold Langford.

In 1920 Lewis returned to Harvard as a professor of philosophy. While teaching he also worked out his theory of conceptual pragmatism, published in Mind and the World-order (1929). According to Lewis, knowledge consists of the conceptual interpretation of the empirically given data of experience. Basic concepts utilized in the interpretation are a priori. However, the mind is not fitted out with a set of categories once and for all, as Immanuel Kant had claimed. Rather, the categories are selected pragmatically—that is, with attention to the ends of action, for which knowledge is gained and into which it issues.

Lewis's lectures before the American Philosophical Association were published as Analysis of Knowledge and Valuation (1946). The book was divided into three parts. The first described Lewis's theory of logic; the second advanced his theory of empirical knowledge; and the last set forth his theory of value judgment. The work stimulated intense discussion and comment in philosophical journals.

After retiring from Harvard in 1953, Lewis joined the Stanford University faculty. He focused on ethics and social philosophy. His 1954 lectures at Columbia University were published as The Ground and Nature of the Right (1955). His lectures at Indiana University were published as Our Social Inheritance (1957).

Lewis died at his home in California on Feb. 3, 1964. His manuscript on ethics, edited by John Lange, was published as Values and Imperatives (1969).

Further Reading

The Philosophy of C. I. Lewis (1968), edited by Paul Arthur Schilpp, is indispensable; it contains Lewis's intellectual autobiography. Andrew J. Reck, The New American Philosophers: An Exploration of Thought since World War II (1968), contains a comprehensive survey of Lewis's thought. Special aspects of Lewis's philosophy are treated in Bella K. Milmed, Kant and Current Philosophical Issues (1961); Chung-ying Cheng, Peirce's and Lewis's Theories of Induction (1969); and J. Roger Saydah, The Ethical Theory of Clarence Irving Lewis (1969). □