19 When these truths are done away with, which are as the principles of nature and important for knowledge and for practical use, it is easy to see what will become of both public and private morality. We say nothing of those more heavenly virtues, which no one can exercise or even acquire without a special gift and grace of God; of which necessarily no trace can be found in those who reject as unknown the redemption of mankind, the grace of God, the sacraments, and the happiness to be obtained in heaven. We speak now of the duties which have their origin in natural probity. That God is the Creator of the world and its provident Ruler; that the eternal law commands the natural order to be maintained, and forbids that it be disturbed; that the last end of men is a destiny far above human things and beyond this sojourning upon the earth: these are the sources and these the principles of all justice and morality. If these be taken away, as the naturalists and Freemasons desire, there will immediately be no knowledge as to what constitutes justice and injustice, or upon what principle morality is founded. And, in truth, the teaching of morality which alone finds favor with the sect of Freemasons, and in which they contend that youth should be instructed, is that which they call "civil," and "independent," and "free," namely, that which does not contain any religious belief. But, how insufficient such teaching is, how wanting in soundness, and how easily moved by every impulse of passion, is sufficiently proved by its sad fruits, which have already begun to appear. For, wherever, by removing Christian education, this teaching has begun more completely to rule, there goodness and integrity of morals have begun quickly to perish, monstrous and shameful opinions have grown up, and the audacity of evil deeds has risen to a high degree. All this is commonly complained of and deplored; and not a few of those who by no means wish to do so are compelled by abundant evidence to give not infrequently the same testimony.
Source: Humanum Genus (Vatican.va)