The Encyclical Rerum Novarum (Of New Things) by Leo XIII, 1891

Leo XIII’s encyclical was the “first social encyclical.” As the “Compendium for the Social Doctrine of the Church” notes (Par. 87), “the Encyclical Letter Rerum Novarum marks the beginning of a new path. Grafting itself onto a tradition hundreds of years old, it signals a new beginning and a singular development of the Church’s teaching in the area of social matters.”

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In other words, this encyclical marks the beginning of what we could call the Church’s “social doctrine.” It’s not that the Church ignored social problems before Leo XIII; rather, with this encyclical, the Church began to speak, from Gospel values, her large doctrinal history, and her wealth of experience, to the social issues and ills of the day.

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To summarize the document would be a tremendous task, so we wish only to point out that, even if it does not do so explicitly, Rerum Novarum lays the basis for the principles of subsidiarity and solidarity. These two principles are cornerstones of the Church’s social teaching.

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Subsidiarity means that action should be taken at the lowest level possible. If, for instance, a family can provide for its children just fine, there is no reason for the state to intervene. If the lower-level falters, then the higher level of authority can come to assist, but the preference is that the lowest level look after its concerns.

Solidarity encourages all to work together, since we are all the Body of Christ.  As Micah D. Kiel points out in his book “Be Transformed , A Biblical Journey toward a More Just World” (pg. 37),  this phrase most often “refers to the mystical body of the church [but it] also applies to the whole of society”). Other documents also cite Leo XIII’s work as the basis for many of the rights developed in later pontifical teachings.