common good a normative standard in Thomistic and Neo-Thomistic ethics for evaluating the justice of social, legal, and political arrangements, referring to those arrangements that promote the full flourishing of everyone in the community. Every good can be regarded as both a goal to be sought and, when achieved, a source of human fulfillment. A common good is any good sought by and/or enjoyed by two or more persons (as friendship is a good common to the friends); the common good is the good of a ‘perfect’ (i.e., complete and politically organized) human community – a good that is the common goal of all who promote the justice of that community, as well as the common source of fulfillment of all who share in those just arrangements. ‘Common’ is an analogical term referring to kinds and degrees of sharing ranging from mere similarity to a deep ontological communion. Thus, any good that is a genuine perfection of our common human nature is a common good, as opposed to merely idiosyncratic or illusory goods. But goods are common in a deeper sense when the degree of sharing is more than merely coincidental: two children engaged in parallel play enjoy a good in common, but they realize a common good more fully by engaging each other in one game; similarly, if each in a group watches the same good movie alone at home, they have enjoyed a good in common but they realize this good at a deeper level when they watch the movie together in a theater and discuss it afterward. In short, common good includes aggregates of private, individual goods but transcends these aggregates by the unique fulfillment afforded by mutuality, shared activity, and communion of persons. As to the sources in Thomistic ethics for this emphasis on what is deeply shared over what merely coincides, the first is Aristotle’s understanding of us as social and political animals: many aspects of human perfection, on this view, can be achieved only through shared activities in communities, especially the political community. The second is Christian Trinitarian theology, in which the single Godhead involves the mysterious communion of three divine ‘persons,’ the very exemplar of a common good; human personhood, by analogy, is similarly perfected only in a relationship of social communion. The achievement of such intimately shared goods requires very complex and delicate arrangements of coordination to prevent the exploitation and injustice that plague shared endeavors. The establishment and maintenance of these social, legal, and political arrangements is ‘the’ common good of a political society, because the enjoyment of all goods is so dependent upon the quality and the justice of those arrangements. The common good of the political community includes, but is not limited to, public goods: goods characterized by non-rivalry and non-excludability and which, therefore, must generally be provided by public institutions. By the principle of subsidiarity, the common good is best promoted by, in addition to the state, many lower-level non-public societies, associations, and individuals. Thus, religiously affiliated schools educating non-religious minority children might promote the common good without being public goods. See also AQUINAS, JUSTICE, POLITICAL PHI- LOSOPHY, SOCIAL PHILOSOPHY, SUBSIDIARITY. J.B.M.