The goods that we pursue in our lives are for us, first and foremost, goods that are particular and personal, and thus goods that are immediate to our attention. Not readily apparent to us are goods necessary for the flourishing of our lives but that can be attained by us only in consort with others and thus realized only through collective action. Such goods are common goods. The wider the good, the more extensive must be the human cooperation to realize the good. A stable, orderly society and a habitable planetary environment are common goods that can be realized only in and through the cooperation of all for the benefit of all. That all contribute to the shared good of the whole is a matter of justice--social justice. Acting for the Common Good undertakes the study of social justice in light of the common good--this from the viewpoint of Catholic social teaching, which draws upon the tradition of the common good that is articulated classically in the philosophy of Aristotle and the theology of Thomas Aquinas and in the modern-day social thought and authoritative teachings of the Catholic Church.