Rather, she comes to the social question when the social question comes to her. The teaching of Scripture with respect to social ethics. The apostolic tradition and the present magisterium of the Church. The experience of the Church and her members throughout history. The relevant findings of the human and social sciences.
Social witness precedes social teaching.
The magisterium, in short, follows the biblical testimony, lived experience, and the scientific knowledge that is the fruit of reflection on that experience. The historical emphasis in both volumes follows from this idea. An example may help. 1 Sheed's point is well-taken, but if witness is to precede doctrine, then using the approach of Charles, one would not expect the Church to develop its teaching on the rights of conscience until those rights were jeopardized. That theme could be traced through the intervening period, as Charles does, examining both high and low points.