As I agreed to review Pope Leo XIII’s famous social encyclical Rerum Novarum of 1891 in the light of his earlier 1888 encyclical Libertas, my immediate expectation was that I would find the social teaching to be dated, whereas the teaching on liberty to be pertinent. It is obvious that with social, economic, and scientific development new challenges are constantly being born. Thus, practical ethical reflection has to be continuously renewed, furthered, and expanded, applying the same moral principles to evermore complex situations, and the greater the velocity of cultural and social changes, the more urgent is the need for an applied, adapted, and relevant social ethics. Moral rules, on the contrary, do not age because human nature in its essence is always the same, and so I imagined that Leo XIII’s defense of liberty would not raise eyebrows. To my surprise, it immediately became clear that it is this teaching that needs to be purified and corrected.
Wojciech Giertych, "Rerum Novarum in the Light of Libertas," Journal of Markets & Morality 19, no. 2 (Fall 2016): 403-416