May 15, 1891 -- Pope Leo XIII defends workers' rights and property rights in the encyclical Rerum novarum

Rerum novarum (from its incipit, with the direct translation of the Latin meaning "of revolutionary change"), or Rights and Duties of Capital and Labor, is an encyclical issued by Pope Leo XIII on 15 May 1891. It is an open letter, passed to all Catholic patriarchs, primates, archbishops and bishops, that addressed the condition of the working classes. It discusses the relationships and mutual duties between labor and capital, as well as government and its citizens. Of primary concern is the need for some amelioration of "the misery and wretchedness pressing so unjustly on the majority of the working class." It supports the rights of labor to form unions, rejects both socialism and unrestricted capitalism, while affirming the right to private property. Rerum Novarum is considered a foundational text of modern Catholic social teaching.

Pope Leo XIII (Public Domain)