HUMAN LIBERTY- 153
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 teach- ing whatever it pleases — a liberty which the State carmot grant without failing in its duty. And the more so, be- cause 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. Wherefore, this liberty also, in order that it may deserve the name, must be kept within certain limits, lest the office of teaching be turned with impunity into an instru- ment of corruption. Now truth, which should be the only subject-matter of those who teach, is of two kinds, natural and supernatural. Of natural truths, such as the principles of nature and whatever is derived from them immediately by our reason, there is a kind of com- mon patrimony in the human race. On this, as on a firm basis, morality, justice, religion, and the very bonds of human society rest : and to allow people to go unharmed who violate or destroy it, would be most impious, most foolish, and most inhuman. But with no less religious care must we preserve that great and sacred treasure of the truths which God Himself has taught us. By many and convincing arguments, often used by defenders of Christianity, certain leading truths have been laid down: namely, that some things have been revealed by God; that the only-begotten Son of God was made flesh, to bear witness to the truth; that a perfect society was founded by Him — the Church namely, of which He is the head, and with which He has proiTiised to abide till the end of the world. To this society He entrusted all the truths which he had taught, in order that it might keep and
