CLIFFORD, WILLIAM KINGDON Eng lish mathematician and philosopher, was born on May 4, at Exeter, where his father was a leading citizen. He was edu cated at King's college, London, and at Trinity college, Cambridge, where he was elected fellow in 1868. In 1871 he was appointed professor of mathematics at University college, London, and in 1874 became fellow of the Royal Society. In 1875 he married Lucy, daughter of John Lane, of Barbados, well known under her married name as a novelist and dramatist. In 1876 Clifford, a man of high-strung and athletic, but not robust, physique, began to fall into ill-health, and after two voyages to the South, died, dur ing the third, of pulmonary consumption at Madeira, on March 3, 1879, leaving his widow with two daughters. Mrs. W. K. Clif ford (d. 1929) earned for herself a prominent place in English literary life as a novelist, and later as a dramatist. Her best-known story, Mrs. Keith's Crime (1885), was followed by several other volumes, the best of which is Aunt Anne (1893) ; and the literary talent in the family was inherited by her daughter Ethel (Lady Fisher Wentworth Dilke), a writer of some charming verse.
Clifford impressed all his contemporaries as a man of extraor dinary acuteness and originality; he had also quickness of thought and speech, a lucid style, wit and poetic fancy, and social warmth. He was a mathematician of the front rank, and contrary to the excessively analytic tendency of the Cambridge mathematicians, "above all and before all a geometer." In his theory of graphs he made fruitful suggestions. He was interested in universal algebra, non-Euclidean geometry and elliptic functions, his papers "Preliminary Sketch of Bi-quaternions" (1873) and "On the Canonical Form and Dissection of a Riemann's Surface" ranking as classics. He also wrote "Classification of Loci" (1878), on algebraic forms and projective geometry.
As a philosopher Clifford's name is chiefly associated with two phrases of his coining, "mind-stuff" and the "tribal self." The latter gives the key to Clifford's ethical view, which explains con science and the moral law by the development in each individual of a "self" which prescribes the conduct conducive to the welfare of the "tribe." Clifford was prominent in the battle between Dar winian science and Victorian theology.
His works, published wholly or in part after his death, are, Elements of Dynamic (1879-87); Seeing and Thinking, popular science lectures (1879) ; Lectures and Essays (introduction by Sir F. Pollock, 1879) ; Mathematical Papers (ed. R. Tucker, intro. by J. S. Smith, 1882) ; and The Common Sense of the Exact Sciences, completed by Professor Karl Pearson (1885).