WALTER L. WALLACE, professor of sociology emeritus, died Sept. 18 in Princeton. He was 88. Wallace’s early research focused on the sociology of education and sociological theory, which he pursued after joining the faculty in 1971. Later he turned his attention to issues of ethnicity, race, and nationality. The author of seven books, including Principles of Scientific Sociology, Wallace received national attention in 2008 when he was identified as Michelle Obama ’85’s thesis adviser. He retired in 2001.