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...