129 Anyone who considers without bias the opportunities and advantages which have recently come to the working classes must admit that they are in great part the result of persistent and effective social measures taken by Catholics in accord with the wise directives and repeated exhortations of Our predecessors. The social teachings of Christianity, then, contain sure and sound principles which will make very adequate provision for the rights of the lower classes if those who endeavor to defend these rights only put those principles into practice.
Source: Ad Petri Cathedram (Vatican.va)