 By the late 1920s, Maritain’s attention began to turn to social issues. Although he had some contact with the Catholic social action movement, Action Française, he abandoned it in 1926 when it was condemned by Pope Pius XI for its nationalistic and anti-democratic tendencies. Nevertheless, encouraged through his friendships with the Russian philosopher Nicholas Berdiaev (beginning in 1924) and Emmanuel Mounier (from 1928), Maritain began to develop the principles of a liberal Christian humanism and defense of natural rights.