48 We must strengthen these convictions in ourselves if we are also to avoid another danger which the desire for reform can produce, not so much in us pastors, who are restrained by the proper awareness of our sacred duty, as in many of the faithful, who think that the reform of the Church should consist principally in adapting its way of thinking and acting to the customs and temper of the modern secular world. The fascination of worldly life today is very powerful indeed, and many people regard conformity to it as an inescapable and indeed a wise course to take. Hence, those who are not deeply rooted in the faith and in the observance of the Church's laws, readily imagine that the time is ripe to adjust themselves to worldly standards of living, on the assumption that these are the best and only possible ones for a Christian to adopt. This craving for uniformity is observable even in the realm of philosophy (it is extraordinary how much weight is attached to fashion in a province where the mind ought to be free and independent, anxious only to arrive at the truth, and bowing to the authority of none but proved masters). It is observable also in the realm of ethics, making it more and more perplexing and difficult to define moral rectitude and the right conduct of life.
Source: Ecclesiam Suam (Vatican.va)