Encyclical Letter Ad Petri Cathedram Nº 6, Author: John XXIII

All the evils which poison men and nations and trouble so many hearts have a single cause and a single source: ignorance of the truth—and at times even more than ignorance, a contempt for truth and a reckless rejection of it. Thus arise all manner of errors, which enter the recesses of men's hearts and the bloodstream of human society as would a plague. These errors turn everything upside down: they menace individuals and society itself.

Second Timothy 4, 1-5

Before God and before Christ Jesus who is to be judge of the living and the dead, I charge you, in the name of his appearing and of his kingdom: proclaim the message and, welcome or unwelcome, insist on it. Refute falsehood, correct error, give encouragement -- but do all with patience and with care to instruct. The time is sure to come when people will not accept sound teaching, but their ears will be itching for anything new and they will collect themselves a whole series of teachers according to their own tastes; and then they will shut their ears to the truth and will turn to myths. But you must keep steady all the time; put up with suffering; do the work of preaching the gospel; fulfil the service asked of you.