The original doctrines were those of the Catholic Church, especially as taught by the so-called doctors (religious scholars) of the Church. But today a doctrine can come from many other sources. Old and established legal principles are called legal doctrine. Traditional psychiatrists still follow the doctrines of Sigmund Freud. Communist doctrine in the 1920s and ʼ30s was often the teachings of Lenin, which were then regarded in the Soviet Union as almost sacred. U.S. presidents have given their names to doctrines as well: In 1823 the Monroe Doctrine stated that the United States would oppose European influence in the Americas, and in 1947 the Truman Doctrine held that America would support free countries against enemies outside and inside.