The following short extract from The New Catholic Encyclopedia (so called because it was new when it appeared in 1967, in the aftermath of the Second Vatican Council) is largely based on Cronin's work, which as you have seen updates the views of Thomas Aquinas in light of recent papal encyclicals and modern social structures such as the class distinction of worker and owner (of the means of production, i.e., the capitalist class). Although this article is posted only at the last minute it is worth reading since it provides a context for the other readings. If you like it, you might look at the entire article, which is much longer than the few paragraphs presented here. In any event, you need not make a class report on this piece since most of it overlaps with the Cronin selection..
In the age of privileged classes and even more in the age of individualism, doctrinal presentations of distributive (and also legal) justice ignored a perspective that has been added in the 20th century, namely, that of justice of the common good, or social justice. Justitia socialis has become recognized as a new and important subspecies of the virtue of justice since Pius XI's encyclical Quadragesimo anno. It includes both legal and distributive justice, and yet its chief concern is not so much strict legal rights and duties as it is the natural rights of the community, its members, and the member communities of the family of nations in their relations to one another.
In keeping with the pressing question of the just social position of the worker, the notion of social justice was first applied basically and primarily to the relation between the owner of capital, the entrepreneur, and the worker as members of various social groups. Among other things, that meant the worker should be paid as a member of a family; that the shares of wages and profits, the allotment of the social products to each, should be computed with an eye toward the good of the industry, the general economy, and the social order.
In an age of steadily increasing economic complexity, of countless interrelations, and a solidarity that extends far beyond particular industries, indeed beyond national economies, it becomes much more apparent than in the ages of household and city economy that the principles of commutative justice alone are entirely insufficient. There is much more involved in every transaction than mere exchange between private parties, for every transaction presupposes countless prior transactions on the part of the society. And ultimately it is not merely a question of transactions and prior transactions. A truly realistic view of justice, achieved only gradually in the modern age, envisions above all the community of persons naturally established by God: the common family of all mankind. Every talent and all possessions are bestowed by God with a view toward the totality. The person unfolds to the highest level of his being only in solidarity. Every form of justice is included in and presupposed by social justice, but in the latter case it is always a question of rights and duties that derive from the nature of the human community and of the person. Transactions are not primary. It is rather the social nature of man that is primary, the encompassing social purpose of all earthly goods, and also the abilities of the person.
The Family. Social justice encompasses every community from the family to the community of nations. The child as a person and as a member of the human community has inalienable rights above all, the right to life (and that indeed from the moment of conception), the right to be born into a wholesome family (from which follow the immorality of extramarital intercourse and a whole set of community obligations for safeguarding the family), and the right to education and support. Every community, from the family on up to the state and the community of nations, has to attend to and, as far as possible, to protect these rights. Because of their parenthood, because of their place in the community, parents owe to the child all that is requisite for healthy physical and spiritual development and for membership in human society. This social obligation depends on their means and on their ability to work, but first and most basically on the fact that they are parents. Similarly, on the basis of his belonging to the family, the child has the obligation, to the extent that it is possible within the family, to be concerned with the progress of the family in every regard and above all to show love for his parents in return for their love. But this is not a debt that could be paid off on the basis of commutative justice. It is the response required by the very nature and position of the child as a member of the family. And it becomes real and urgent also if and perhaps only if other members of the family are remiss.
Civil Government. Beginning with the smaller groups and next higher communities and extending on up to the state and the community of nations, the government has the duty of safeguarding the inalienable rights of each member of the community. Such rights would be, for example, the rights to life, security, intellectual and religious freedom, and the opportunity to work according to one's capacity, so long as one does not forfeit one or the other of these rights by wrongdoing, thus bringing into play penal justice.
Social justice demands that neither the person nor the group be deprived of its proper functions. On the contrary, the fundamental principle of subsidiarity a typical expression of social justice requires the higher community, from the family on up, to do all that it can to preserve the functional integrity of the lower community and the person and also, if necessity forces it to take over the lower role, to reestablish it, having taken on this function only temporarily and as a substitute measure. Conversely, the person and the group must be constantly prepared to preserve the functional integrity of every higher group and of society as a whole at their own levels.
International Community. In mid-20th century the solidarity of the community of nations has strongly come to the fore. Through the development of modern technology and culture, nations have grown more closely together and now demonstrate in very many ways that the general welfare of each nation individually and of all nations collectively are closely linked. Catholic social teaching (above all, Mater et Magistra, Pacem in terris, and the Constitution of Vatican Council II On the Church and the Modern World) has made a decisive contribution to the further development of a worldwide view of common welfare justice. The nations especially favored by nature and history are obliged to come to the aid of the poor nations seeking further technological and cultural advancement, until the poor nations reach their full functional capacity and corresponding autonomy within the community of nations. Aid for development and promoting practicable possibilities for emigration are not charitable "alms" but rather actual demands of the social order and duties in justice for the sake of peace. Such help should not be made to depend on repayment, which is often quite impossible.
Boundaries between Justice and Love. Social justice presupposes deep insight into the social nature of man and into the essential purpose of the different types of community. The boundaries between justice and love are drawn strictly or more loosely, depending on the situation. Much of what was seen in the past as a mere "duty of love" or as gratuitous almsgiving is now clearly seen as a requirement of social justice if one considers the essential solidarity of the family of mankind. This advancement approximates the view of the Church Fathers (despite differences in social and economic structures and in the tasks at hand), who, moreover, saw this essential solidarity not from the viewpoint of justice among men but from the perspective of divine justice and evangelical love. Finally, social justice can endure in its full breadth and height only in terms of faith in God, the giver of all good gifts, and in the unity of the human race in God's sight. It is the familial justice of the creatures of God and the children of God, the basic attitude of the "family of God."
Such an approach to social justice in no way allows men to be self-satisfied after the manner of those who are just according to the law. It is an essentially dynamic view that keeps them aware of the perpetually approximative and imperfect character of every fulfillment. It attempts to take the next step that is historically possible at any given time.
(From "Justice," in The New Catholic Encyclopedia, Vol 7, 1967)