Rerum Novarum (Latin for On the New Things) is an encyclical issued by Pope Leo XIII on May 15, 1891. It was an open letter, passed to all Catholic bishops, that addressed the condition of the working classes. The encyclical is entitled: "Rights and Duties of Capital and Labour". Wilhelm Emmanuel von Ketteler and Cardinal Henry Edward Manning were influential in its composition.
It discussed the relationships and mutual duties between labour and obtaining capital, as well as government and its citizens. Of primary concern was the need for some amelioration for "The misery and wretchedness pressing so unjustly on the majority of the working class." It supported the rights of labor to form unions, rejected communism and unrestricted capitalism, whilst affirming the right to private property.
Many of the positions in Rerum Novarum were supplemented by later encyclicals, in particular Pius XI's Quadragesimo Anno (1931), John XXIII's Mater et Magistra (1961), and John Paul II's Centesimus Annus (1991).
Read more about Rerum Novarum: Message, Impact and Legacy, Highlights of The Encyclical