Pope Leo XIII wrote the papal encyclical Rerum Novarum in 1891. Rerum Novarum represents the first papal encyclical devoted to Catholic social teaching, or church teachings that address social, economic, and ecological justice. Pope Leo XIII had been trained in Thomistic philosophy and theology (the teachings of Saint Thomas Aquinas). He thus addressed various matters of contemporary concern from within this framework. There are two major inspirations for his writing Rerum Novarum. The first concerns the injustices that emerged during and after the Industrial Revolution (roughly 1760– 1840). The second has to do with the rise of communism in the 1840s. Leo does not refer explicitly to communism, but he has that in mind when he refers to “socialism,” which is where communism came from. In 1848 Karl Marx and Friedrich Engels published the first edition of The Communist Manifesto, which addressed many of the themes Pope Leo XIII would later discuss in Rerum Novarum. Pope Leo XIII felt obligated to provide a Catholic response to the ills that afflicted humanity in the wake of both the Industrial Revolution and the rise of communism. He found the capitalist response and the communist response both wanting. Neither the focus on capital and private property nor the emphasis on the community was sufficient to capture what was at stake with the natural rights that Pope Leo XIII taught were God-given.