Stuart MacDonald Brown Jr., a former Cornell administrator and professor who was an authority on the philosophy of ethics and political theory, died March 18 at the Reconstruction Home in Ithaca, N.Y. He was 80.

He died from complications of a stroke, said his wife, Catherine D. Hemphill.

Brown spent nearly all his professional life in university teaching and administration. He taught philosophy at Cornell from 1946 to 1970, served as dean of the College of Arts and Sciences from 1964 to 1969 and as vice president for academic affairs from 1968 to 1970.

Brown left Cornell to become vice president for academic affairs at the University of Hawaii in 1970. He returned to Cornell in 1974 as professor and retired from the faculty in 1981.

While at Cornell, Brown oversaw the development of a new major, biology and society. The major, which still is offered, combines training in biology with the exposure to perspectives from the social sciences and humanities on the political, social and ethical aspects of modern biology.

He earned his bachelor's and doctoral degrees from Cornell in 1937 and 1942, respectively.

He served in the U.S. Army Signal Corps from 1943 to 1946, attaining the rank of master sergeant.

Brown was managing editor of The Philosophical Review from 1950 to 1954 and from 1959 to 1961. He was a regular contributor to such journals as The Review, the Journal of Philosophy and Ethics.

He also wrote for the American Kennel Gazette, drawing on his expertise and interest in philosophy and dogs. He and his wife showed and bred giant schnauzers.

Brown was born in Concord, N.C., and grew up in Camp Hill, Pa., and Indianapolis before moving to Ithaca in the 1930s.

In addition to his wife, Brown is survived by a son, James, of Corrales, N.M.; and two daughters, Deborah New of Canastota, N.Y.; and Margaret Cassiday of Putney, Vt. A son, Peter, died in 1981.

In lieu of flowers, contributions may be sent to the Reconstruction Home, 318 S. Albany St., Ithaca, N.Y., or to the SPCA, 1640 Hanshaw Road, Ithaca.