Papal letters to the Universal Church or, in many cases, especially before Vatican II, to the Bishops in communion with the Holy See. Worthy of special attention besides Rerum Novarum (see previous post) are Quadragesimo Anno, Mater et Magistra, Pacem in Terris, Populorum Progressio, Laborum Exercens, Sollicitudo Rei Socialis, Centesimus Annus, Caritas in Veritate, Fides et Ratio, and Spe Salvi. As of this post, the Vatican has online the encyclicals of Leo XIII, Pius X, Benedict XV, Pius XI, Pius XII, John XXIII, Paul VI, John Paul II, Benedict XVI, and Francis. ISBN recommendation: 0-87650-259-1
Pope Leo XIII, seeking to address “the misery and wretchedness pressing so unjustly on the majority of the working class”, issued on 15 May 1891 Rerum Novarum, an encyclical on the rights and duties of capital and labor. It is considered a seminal classic of Catholic social teaching. Image links to Vatican translation.