This Element examines the historical context and intellectual implications of the Thomistic revival inaugurated by Pope Leo XIII's encyclical Aeterni Patris, pursuing two principal objectives. First, this Element demonstrates that Aeterni Patris represented a decisive turning point in Catholic philosophical and theological thought: it not only revitalised Thomism but also brought an end to the doctrinal pluralism that had characterized nineteenth-century Catholicism. Second, the study argues that the Thomistic revival envisioned by Leo XIII was not a neutral academic enterprise concerned merely with a renewed engagement with Aquinas's doctrine, but rather an ideological initiative rooted in the framework of intransigent Catholicism, wherein the restoration of Thomism was conceived as instrumental to the formation of a new Christian worldview.