Percy Brand Blanshard was born August 27, 1892 in Fredericksburg, Ohio. His father, Francis, a Congregational minister, and his mother, Emily Coulter Blanshard, were both Canadians by birth and naturalized American citizens.

As an undergraduate, Blanshard studied at the University of Michigan while majoring in classics. After three years at Michigan, he obtained a Rhodes Scholarship to study at Oxford University, where he studied under Horace W.B. Joseph and also met F.H. Bradley and T.S. Eliot. At the outbreak of World War I Blanshard interrupted his studies to join the British Army YMCA, which sent him to Bombay and Amhara. Eventually, submarine warfare forced him to return to the United States via Japan. Stateside, he earned an M.A. at Columbia University studying under W.P. Montague and meeting John Dewey. After Columbia, he joined the US Army, serving in France. Once demobilized, he returned to Oxford to complete his BA (Hons), and then did his doctorate at Harvard under Clarence Irving Lewis.

After teaching at Michigan a short time, he taught at Swarthmore College, 1925-1944. He then spent the remainder of his career until his retirement in 1961 at Yale University, where he served as chairman of the Department of Philosophy for many years. In 1952, he delivered the Gifford Lectures in Scotland. As for his personal life, in 1918, Blanshard married Frances Bradshaw. Frances died in 1966 and in 1969 he married Roberta Yerkes, a daughter of his Yale colleague Robert M. Yerkes.

Blanshard was a rationalist who professed and defended conceptions of reason during a century when reason came under philosophical attack. He also held, unlike what he termed ‘younger men brought up in linguistic and analytic schools of thought’, that Christian dogmas are neither meaningless nor merely superstitions of a pre-critical age (Reason and Belief 9). In 1952 and 1953 Blanshard delivered the Gifford lectures at St. Andrews, in which he discussed the position of reason in the theory of knowledge in ethics and theology. His lectures later became part of a three volume work: Reason and Analysis (1962), Reason and Goodness (1961), and Reason and Belief (1975), respectively. The second and third volumes were initially based on a the William Belden Noble Lectures delivered at Harvard University in 1948 and then incorporated into the Gifford series by the permission of the Harvard Board of Preachers. The first volume, Reason and Analysis, is based in part on the Carus Lectures presented to the American Philosophical Association in 1959.

Blanshard died, at the age of 95, on November 19, 1987, in New Haven, Connecticut.

Other books by Blanshard include Church and the Polish Immigrant (1920), In Commemoration of William James 1842-1942 (1942), Philosophical Analysis (1952), On Philosophical Style (1954), Impasse in Ethics and a Way Out (1955), Education in the Age of Science (1959), The Nature of Thought (1964), Four Reasonable Men (1984) that contains sympathetic biographical accounts of four exemplars of the rational temper: Marcus Aurelius, John Stewart Mill, Ernest Renan, and Henry Sidgwick.