Neo-Thomism a philosophical-theological movement in the nineteenth and twentieth centuries manifesting a revival of interest in Aquinas. It was stimulated by Pope Leo XIII’s encyclical Aeterni Patris (1879) calling for a renewed emphasis on the teaching of Thomistic principles to meet the intellectual and social challenges of modernity. The movement reached its peak in the 1950s, though its influence continues to be seen in organizations such as the American Catholic Philosophical Association. Among its major figures are Joseph Kleutgen, Désiré Mercier, Joseph Maréchal, Pierre Rousselot, Réginald Garrigou-LaGrange, Martin Grabmann, M.-D. Chenu, Jacques Maritain, Étienne Gilson, Yves R. Simon, Josef Pieper, Karl Rahner, Cornelio Fabro, Emerich Coreth, Bernard Lonergan, and W. Norris Clarke. Few, if any, of these figures have described themselves as Neo- Thomists; some explicitly rejected the designation. Neo-Thomists have little in common except their commitment to Aquinas and his relevance to the contemporary world. Their interest produced a more historically accurate understanding of Aquinas and his contribution to medieval thought (Grabmann, Gilson, Chenu), including a previously ignored use of the Platonic metaphysics of participation (Fabro). This richer understanding of Aquinas, as forging a creative synthesis in the midst of competing traditions, has made arguing for his relevance easier. Those Neo-Thomists who were suspicious of modernity produced fresh readings of Aquinas’s texts applied to contemporary problems (Pieper, Gilson). Their influence can be seen in the revival of virtue theory and the work of Alasdair Mac- Intyre. Others sought to develop Aquinas’s thought with the aid of later Thomists (Maritain, Simon) and incorporated the interpretations of Counter-Reformation Thomists, such as Cajetan and Jean Poinsot, to produce more sophisticated, and controversial, accounts of the intelligence, intentionality, semiotics, and practical knowledge. Those Neo-Thomists willing to engage modern thought on its own terms interpreted modern philosophy sympathetically using the principles of Aquinas (Maréchal, Lonergan, Clarke), seeking dialogue rather than confrontation. However, some readings of Aquinas are so thoroughly integrated into modern philosophy that they can seem assimilated (Rahner, Coreth); their highly individualized metaphysics inspired as much by other philosophical influences, especially Heidegger, as Aquinas. Some of the labels currently used among Neo-Thomists suggest a division in the movement over critical, post- Kantian methodology. ‘Existential Thomism’ is used for those who emphasize both the real distinction between essence and existence and the role of the sensible in the mind’s first grasp of being. ‘Transcendental Thomism’ applies to figures like Maréchal, Rousselot, Rahner, and Coreth who rely upon the inherent dynamism of the mind toward the real, rooted in Aquinas’s theory of the active intellect, from which to deduce their metaphysics of being. See also AQUINAS , GILSON , MARITAIN , MERCIER , THOMIS. D.W.H.