Libertas §24

²⁴ A like judgment must be passed upon what is called liberty of teaching. There can be no doubt that truth alone should imbue the minds of men, for in it are found the well-being, the end, and the perfection of every intelligent nature; and therefore nothing but truth should be taught both to the ignorant and to the educated, so as to bring knowledge to those who have it not, and to preserve it in those who possess it. For this reason it is plainly the duty of all who teach to banish error from the mind, and by sure safeguards to close the entry to all false convictions. From this it follows, as is evident, that the liberty of which We have been speaking is greatly opposed to reason, and tends absolutely to pervert men's minds, in as much as it claims for itself the right of teaching whatever it pleases - a liberty which the State cannot grant without failing in its duty. And the more so because the authority of teachers has great weight with their hearers, who can rarely decide for themselves as to the truth or falsehood of the instruction given to them.