Quadragesimo anno was issued by Pope Pius XI, on 15 May 1931, 40 years after Rerum novarum. Unlike Leo, who addressed mainly the condition of workers, Pius XI concentrated on the ethical implications of the social and economic order. He called for the reconstruction of the social order based on the principle of solidarity and subsidiarity.[203] He noted major dangers for human freedom and dignity, arising from unrestrained capitalism and totalitarian communism.