25 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 instrument 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 common 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.
Source: Libertas (Vatican.va)