Catholic reflections on social inequality usually begin with modern social encyclicals, while the political-theological frameworks shaping their conceptual boundaries remain largely neglected. Examining 19th-century Catholic political theology is therefore not only of historical interest but also clarifies the assumptions behind the Church's responses to inequality. In this context, Juan Donoso Cortés's political theology is especially relevant. Although he did not develop a formal social doctrine, his reflections on the theologically grounded order and the moral limits of political rationality influenced later encyclicals and illuminate the Catholic understanding of equality and justice. In Donoso's thought, equality appears primarily on a moral-theological rather than a political level. His thinking centers on original sin, which denies that sinful humanity can create a perfectly governed and socially equal society. He rejects revolutionary egalitarianism rooted in Enlightenment ideals that elevate legal equality to an absolute principle and seek to impose it through radical means. Donoso interprets this as theological rebellion: a sinful overemphasis on human autonomy and a turning away from divine order. He accepts only a limited but fundamental equality: the moral and theological equality of all persons before God. This cannot lead to social equality, since social inequalities follow necessarily from fallen human nature and cannot be eliminated by legal or social reforms alone. This distinction contributed to the Catholic tradition's emphasis on moral order over egalitarian promises. Donoso's arguments indirectly influenced Pope Pius IX's critique of modernity, especially the logic of the Syllabus, and later shaped the moral-anthropological framework within which Pope Leo XIII addressed social inequality in Rerum Novarum.