We thought we were finished with this discussion, but again our commentator came back. She claimed she had read Father Ferree's Introduction to Social Justice . . . but didn't understand what we meant by "social justice," nor "equality of status." This tends to suggest, of course, that she didn't really read Introduction to Social Justice, at least in the sense that Mortimer Adler meant it in How to Read a Book. Today we'll address what we mean by social justice, and then finish off by explaining why equality of status is so important in carrying out acts of social justice.
It's actually pretty straightforward. Social justice is the virtue directed at the common good, which in this context is the vast network of institutions within which humanity as "political animals" acquire and develop virtue — habits of doing good.
It is this capacity to acquire and develop virtue that defines us as human beings. Virtue, in fact, signifies "human-ness." The problem is that in traditional individualistic philosophy, nobody has the power to access the common good directly. It can only be affected indirectly (so traditional philosophers tell us) by people being individually virtuous, thereby setting the general "tone" of society which guides the functioning of institutions and how well they do their jobs. If people are virtuous, society will function properly.
Except that it doesn't. Leo XIII realized that if we want to affect our institutions, we must act institutionally, that is, socially. We can't do it as individuals. We can only affect the common good directly as members of groups. Otherwise, we can all be personally virtuous, but our badly designed or flawed institutions prevent society from working.
Pius XI's breakthrough in moral philosophy was to take the techniques of social justice described by Leo XIII and develop a completed doctrine of social justice — the discernment of a particular "act" of social justice by means of which we can access the common good directly. This was to respond to the traditional philosophers who continued to insist that Leo XIII couldn't possibly have meant what he said, for it was clearly impossible. As Pius XI explained,
"The redemption of the non-owning workers — this is the goal that Our Predecessor declared must necessarily be sought. And the point is the more emphatically to be asserted and more insistently repeated because the commands of the Pontiff, salutary as they are, have not infrequently been consigned to oblivion either because they were deliberately suppressed by silence or thought impracticable although they both can and ought to be put into effect." (Quadragesimo Anno, § 59.)