Opposition to Socialism and Communism in Catholic social teaching had already been expressed in the teachings of popes since the encyclicals Nostis et nobiscum (1849), Quanta cura (1864), and Rerum novarum (1891).
Penentangan Sosialisme dan Komunisme dalam pengajaran sosial Katolik mulai ditunjukkan dalan pengajaran para paus sejak ensiklik Nostis et nobiscum (1849), Quanta cura (1864), dan Rerum novarum (1891).