# Pope Pius XI **Summary.** Achille Ratti served as pope from 1922 to 1939. He is known in social teaching for the encyclical *Quadragesimo Anno* (1931), which gave the principle of subsidiarity its classic statement. That principle remains a core term in [[Catholic Social Doctrine]]. ## Substance *Quadragesimo Anno* ("In the Fortieth Year") marked forty years since Leo XIII's *Rerum Novarum* (1891). Pius XI revisited the earlier document's treatment of labor, capital, and the social order during the economic crisis of the early 1930s. The encyclical articulated subsidiarity: the idea that a higher or larger body should not absorb functions that a smaller or more local body can handle well. Larger institutions exist to help smaller communities, not to replace them. This became a standard reference point in later Catholic social thought. This page keeps to uncontested public record: the dates of his papacy and his authorship of *Quadragesimo Anno* and its statement of subsidiarity. He issued other encyclicals during his pontificate, but those fall outside this page's narrow scope. ## Why it matters in this wiki Subsidiarity gives the wiki's Catholic-social-teaching thread a specific tool for thinking about power and scale in institutions — including how authority concentrates or distributes in church structures. ## Related - [[Catholic Social Doctrine]]