49 In addition we are confronted with the doctrine of Naturalism, which attempts to undermine the fundamental conception of Christianity. Relativism, too, seeks to justify everything, and treats all things as of equal value. It assails the absolute character of Christian principles. We are also confronted with the growing tendency to prune away from the Christian life everything that requires effort or causes inconvenience. It rejects as vain and futile the practice of Christian asceticism and the contemplation of the things of God. Indeed, sometimes even the apostolic desire for a ready passport into secular society and the determination to make oneself acceptable to men and particularly to the youth of today, prompts certain people to lay aside the principles which characterize our faith and to reject the sort of dignity which gives meaning and force to our determination to make contact with others and makes our teaching effective. Is it not, perhaps, true that some of the younger clergy and religious, in their laudable endeavor to come closer to the masses and to particular groups, aim at becoming like them rather than different from them? By this worthless imitation they forfeit the real value and effectiveness of their endeavors. We must be in the world, but not of it. These important words of Christ are especially relevant at the present time, difficult though they may be to put into practice. It will be well for us if Christ, who lives always to make intercession for us, (31) includes us moderns in the wonderful prayer He addressed to His heavenly Father: "I pray not that thou shouldst take them out of the world, but that thou shouldst keep them from evil." (32)
Source: Ecclesiam Suam (Vatican.va)