What naturalists or rationalists aim at in philosophy, the supporters of liberalism, carrying out the principles laid down by naturalism, are attempting in the domain of morality and politics. The fundamental doctrine of rationalism is the supremacy of the human reason, which, refusing due submission to the divine and eternal reason, proclaims its own independence, and constitutes itself the supreme principle and source and judge of truth. Hence, these followers of liberalism deny the existence of any divine authority to which obedience is due, and proclaim that every man is the law to himself; from which arises that ethical system which they style independent morality, and which, under the guise of liberty, exonerates man from any obedience to the commands of God, and substitutes a boundless license. The end of all this it is not difficult to foresee, especially when society is in question. For, when once man is firmly persuaded that he is subject to no one, it follows that the efficient cause of the unity of civil society is not to be sought in any principle external to man, or superior to him, but simply in the free will of individuals; that the authority in the State comes from the people only; and that, just as every man's individual reason is his only rule of life, so the collective reason of the community should be the supreme guide in the management of all public affairs. Hence the doctrine of the supremacy of the greater number, and that all right and all duty reside in the majority. But, from what has been said, it is clear that all this is in contradiction to reason. To refuse any bond of union between man and civil society, on the one hand, and God the Creator and consequently the supreme Law-giver, on the other, is plainly repugnant to the nature, not only of man, but of all created things; for, of necessity, all effects must in some proper way be connected with their cause; and it belongs to the perfection of every nature to contain itself within that sphere and grade which the order of nature has assigned to it, namely, that the lower should be subject and obedient to the higher.
--Pope Leo XIII,
Libertas Praestantissimum, 1888
