Rerum Novarum:An encyclical issued by Pope Leo XIII in 1891 that addressed the rights of workers and the responsibilities of employers, marking a significant moment in Catholic social teaching.
Vatican I:The First Vatican Council (1869-1870) was convened by Pope Pius IX and set the stage for the strengthening of papal authority, which Leo XIII built upon during his papacy.
Social Catholicism: A movement within the Catholic Church that seeks to apply Christian principles to social, economic, and political issues, significantly influenced by the teachings of Pope Leo XIII.