A major Christian theme that Pius XI highlights in Quadragesimo Anno is the importance of tradition. Pius recognizes that his insights have largely benefited from Rerum Novarum and the forty years of discussion that have resulted from Leo’s foundational work. Rather than writing as if he were the sole source of his reflections, Pius, through his format, acknowledges his debt to the tradition that has preceded him. The first quarter of the work is a summary of Leo’s work, and the remainder of Pius’s encyclical provides clarifications and updates of issues discussed by Leo.
By using Rerum Novarum as a foundation, Pius solidifies certain principles in the tradition of Christian social ethics. He explains that church leaders have the responsibility to speak on moral issues. He clearly explains that private property has both an individual and communal character. He gives fuller consideration to matters central to the determination of a just wage. He also maintains the importance of intermediary associations and formulates the principle of subsidiary function, which later becomes a central principle of the tradition.
In addition, Pius engages in the church’s ongoing dialogue with economic liberalism and socialism. He critiques unbridled liberal economies. He also proposes that socialism, as he defines it, is in itself contrary to the Christian faith. Finally, Pius recalls the ultimate destiny of humankind and the priority of remaining in God’s grace over the accumulation of material wealth. His reflections engage the social structures of his time and encourage further clarification of Christian social principles. Pius’s decision to explicitly acknowledge the social tradition that precedes him is repeated by many who follow him as the bishop of Rome.