Simon studied under Jacques Maritain at the Institut Catholique de Paris. He taught at the Institut Catholique de Lille from 1930 to 1938. In 1938, he came to the University of Notre Dame in South Bend, Indiana, as a visiting professor. He was unable to return to France because of World War II, and after the war he remained as a professor at Notre Dame until 1948. He then joined the Committee on Social Thought, at the University of Chicago. He remained at the University of Chicago until his death. In 1975, Maurice Cranston called him one of the world's "most original and distinguished political theorists."