Article abstract: One of the leading American philosophers of his generation, Lewis responded to developments in logic and science by combining philosophical analysis with pragmatism. He also drew renewed attention to Kantian ethics.
Clarence Irving Lewis grew up in small Massachusetts towns and in the White Mountains of New Hampshire. Later he commented that mountains and deep woods had always had special meaning for him. His parents were orthodoxly religious. His father, who worked in a shoe factory, was quiet and thoughtful and had strong convictions concerning social betterment. He belonged to the Temperance movement, admired Fabian socialism, and joined the Knights of Labor. After involvement in a strike, he was blacklisted by the employers, losing both his job and his home. The family was condemned to years of meager existence.
To help his family, C. I. Lewis early began to undertake part-time and summer farm and factory work. When he was thirteen, he started to think speculatively about the cosmos, questioning the biblical account of it. He later described this as the period of the most intense and furious thinking he ever experienced, his native skepticism clashing explosively with his orthodox upbringing. When he was fifteen and doing summer farm work in the White Mountains, his employer, an elderly woman, encouraged him by revealing that she too had heretical thoughts and by listening at length to his. A year or two later, he began to read about the history of Greek philosophy and found that many of his speculations had been anticipated by the pre-Socratics.
Lewis received a solid education at the public high school of Haverhill and determined to go on to college. He entered Harvard in 1902. Tuition at that time was $150 per year; he had accumulated enough savings from his earlier work so that he was able to enter, and by continuing to do part-time work as a waiter and tutor, he was able to pay his way. He hastened to take his bachelor’s degree in three years, however, to minimize expense.
At Harvard, President Charles W. Eliot’s system of free electives was in place, and Lewis chose to study mainly philosophy. This was the golden age of Harvard philosophy, and his professors included philosophers and psychologists such as Josiah Royce, William James, Hugo Münsterburg, and later George Santayana and Ralph Barton Perry. It was Royce whom Lewis described as his own paradigm of a philosopher; Lewis admired what he called Royce’s ponderous cogency and respected Royce’s absolute idealism, though he did not accept it.
After completing his undergraduate program, Lewis found work as a teacher of English for three years. During this period he married his high-school sweetheart, and soon their first child was born. In 1908, Lewis returned to Harvard for graduate work in philosophy, again studying speedily in order to save money. He earned his doctoral degree in 1910, and in 1911 he secured a teaching position in philosophy at the University of California, Berkeley.
At Harvard, Royce had encouraged Lewis to study new developments in symbolic and mathematical logic, and at Berkeley, Lewis began teaching in this area. Feeling the need for a better textbook, he set out to write A Survey of Symbolic Logic. This was a useful contribution at the time but in 1932 was superseded by Symbolic Logic, which Lewis wrote in collaboration with C. H. Langford. Both books devoted most of their space to presenting in accessible form results originated by others.
There is, however, one new contribution to logic that Lewis introduced in these books: the theory of what he called “strict implication.” This was in opposition to philosopher Bertrand Russell, who had studied the truth-functional conditional, which he had called “material implication.” A truth-functional conditional with false antecedent is true regardless of whether its consequent is true; Russell had confusingly expressed this point by saying that a false proposition implies any proposition. Lewis was incensed at this, because in the usual language of logic, to say that one proposition implies another is to say that the latter can validly be inferred from the former; however, it is not true in general that from a false proposition one may validly infer every proposition.
Lewis’s response was to introduce the notion of strict implication and to construct a formal system for it. Strict implication is the relation that holds between one proposition and another when, if the former is true, the latter must with logical necessity also be true. Lewis drew up sets of axioms for the theory of strict implication, employing also the correlative notion of possibility: a proposition being understood to be possible in this sense when and only when its negation is not logically impossible. In Lewis’s system, an impossible proposition does strictly imply any proposition, but no proposition strictly implies others merely because of its falsity. Lewis had begun the branch of logic that has come to be called “modal logic.”
In 1920, Lewis was called back to Harvard to join its philosophy faculty. He remained until his retirement in 1953. Lewis became an admired teacher at Harvard, noted for his eloquence in courses on the theory of knowledge and on Immanuel Kant’s philosophy. Tall and dignified, usually in a tweed suit, he had a mustache and often wore a pince-nez.
Lewis’s position as a significant American philosopher rests primarily on two large works, Mind and the World-Order and An Analysis of Knowledge and Valuation. Both books deal mainly with...
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