And, though at the present day, owing to the decay of religious belief, this authority cannot be exercised in the same way as of old, it is on that very account all the more necessary for us to bear well in mind, and to carry out fully in practice, the great unchanging principles on which the legislation of the Church in this matter has been ever based.
You are bound, dear children in Jesus Christ, to guard yourselves against all those things which may be a source of danger to your faith or purity of heart.

You have no right to tamper with the one or the other.

Therefore, in the first place, it is the duty of Catholics to abstain from reading all such books as are written directly with the object of attacking the Christian Faith, or undermining the foundations of morality.

If men of learning and position are called upon to read such works in order to refute them, they must do so with the fear of God before their eyes.

They must fortify themselves by prayer and spiritual reading, even as men protect themselves from contagion, where they have to enter a poisonous atmosphere.