Liberalism of every degree and all forms has been formally condemned; so much so that outside of the motives of its intrinsic malice, it stands under the formal ban of the Church, which is sufficient for all faithful Catholics. It would be impossible for an error so widespread and so radical to escape condemnation.
Upon its appearance in France at the time of the Revolution [1789-1799], the famous Declaration of the Rights of Man-----which contains in germ all the follies of Liberalism-----was condemned by Pius VI [1775-1799]. Later the baneful doctrine infected all the countries of Europe. In Spain it first took the name of Liberalism, under which it has since been known everywhere.
Upon the occasion of the appearance of the first errors of De Lamenais, Gregory XVI [1831-1846], in his Encyclical Mirari Vos explicitly condemned Liberalism, as it was then understood, taught, and practiced by the constitutional governments of Europe. Later on, when the full tide of the deplorable deluge had submerged all Europe, carrying all before it, God raised up to His Church Pius IX [1846-1878], who has justly passed into history as the "Scourge of Liberalism."
Liberal error under all its forms, shapes, and shades has been unmasked by this Pope. That his words might carry, as it were, more authority on this question, Providence has willed that these reiterated condemnations of Liberalism should fall from the lips of a Pontiff who, at the beginning of his pontificate, was hailed by Liberalists as their own. But he left no refuge to which their error might have resort. The numerous Briefs and Allocutions of Pius IX have clearly shown to Christian peoples what this baneful heresy is, and The Syllabus of Errors  has put on the final seal of condemnation. Let us see the principal contents of some of the Pontifical documents. Amongst all that we might place before our readers, we will cite only a few.
On the 18th of June, 1871, responding to a deputation of French Catholics Pius IX spoke thus:
"Atheism in legislation, indifference in matters of religion and the pernicious maxims which go under the name of Liberal Catholicism are the true causes of the destruction of the States; they have been the ruin of France. Believe me, the evil I denounce is more terrible than the Revolution, more terrible even than The Commune. I have always condemned Liberal Catholicism and I will condemn it again forty times over if it be necessary."
In a Brief, 6th of March, 1873, addressed to the Circle of St. Ambrose of Milan, the Sovereign Pontiff thus expresses himself:
"People are not wanting who pretend to form an alliance between light and darkness, and to associate justice with iniquity in favor of those doctrines called Liberal Catholicism, which based on the most pernicious principles, show themselves favorable to the intrusion of secular power upon the domain of spirituals; they lead their partisans to esteem, or, at least, to tolerate iniquitous laws, as if it were not written that no one can serve two masters. Those who thus conduct themselves, are more dangerous and more baneful than declared enemies, not only because, without being warned of it, perhaps even without being conscious of it, they second the projects of wicked men, but also because, keeping within certain limits, they show themselves with some appearance of probity and sound doctrine. They thus deceive the indiscreet friends of conciliation and seduce honest people, who would otherwise have strenuously combated a declared error."
In the Brief of the 8th of May of the same year speaking to the Confederation of the Catholic Circle of Belgium, the same Holy Father said:
"What we praise above all in your religious enterprise is the absolute aversion which, as we are informed, you show towards the principles of Liberal Catholicism and your intrepid determination to root them out as soon as possible. In truth you will extirpate the fatal root of discord and you will efficaciously contribute to unite and strengthen the minds of all in so combating this insidious error, much more dangerous than an open enemy because it hides itself under the specious veil of zeal and of charity, and in so endeavoring to protect the people in general from its contaminating influence. Surely you, who adhere with such complete submission to all decisions of this Apostolic Seat and who know its frequent reprobations of Liberal principles, have no need of these warnings."
In the Brief to the La Croix, a Belgium journal, on the 24th of May, 1874, the Pope thus expresses himself thus:
"We cannot do less than to praise the design expressed in this letter, which we know your journal will satisfactorily fulfill, the design to publish, to spread, to comment on and inculcate in all minds all that the Holy See teaches against the perverse or at least false doctrines professed in so many quarters, and particularly against Liberal Catholicism, bitterly striving to conciliate light with darkness and truth with error."
On the 9th of June, 1873, Pius IX wrote to the president of the Council of the Catholic Association of Orleans, and without mentioning its name, depicts pietistic and moderated Liberalism in the following terms:
"Although you have not, strictly speaking, to combat impiety, are you not perhaps menaced on this side by as great dangers as those of the group of friends deceived by that ambiguous doctrine, which, while rejecting the last consequence of error, obstinately retains the germs, and which, not willing to embrace the truth in its fullness, and not daring to abandon it entirely, exhausts itself in interpreting the traditions and teachings of the Church by running them through the mold of its own private opinions."
In an address to the Bishop of Quimper, and speaking in reference to the general assembly of the Catholic Association of that diocese, the Pope said:
"Assuredly these associations are not wanting in the obedience due to the Church, neither on account of the writings nor the actions of those who pursue them with invectives and abuse; but they might be pushed into the slippery path of error by the force of those opinions called Liberal; opinions accepted by many Catholics who are otherwise honest and pious, and who, even by the very influence which gives them their piety, are easily captivated and induced to profess the most pernicious maxims. Inculcate, therefore, Venerable Brother, in the minds of this Catholic assembly that, when we have so often rebuked the sectaries of these Liberal opinions, we have not had in view the declared enemies of the Church, whom it would have been idle to denounce, but rather that those, of whom we are speaking, are such as secretly guard the virus of Liberal Principles which they have imbibed with their mother's milk. They boldly inoculate this virus into the people's minds, as if it were not impregnated with a manifest malice, and as if it were as harmless to religion as they think. They thus propagate the seed of those troubles which have held the world in revolution so long. Let them avoid these ambuscades. Let them endeavor to direct their blows against this perfidious enemy, and certainly they will merit much from their religion and their country."
With these utterances from the mouth of the Vicar of Jesus
friends as well as our enemies must see that the Pope has said in
briefs, and particularly in the last citation, in a general way all
can be said on this question, which we are studying in its details.