Quanta cura (Latin for "With how great care") was a papal encyclical issued by Pope Pius IX on 8 December 1864.

In August 1863, Count Charles Montalembert, a proponent of Liberal Catholicism gave a series of speeches in Mechelen, Belgium, in which he presented his view of the future of modern society and the Church.

At the end of March 1864, he received a letter from Cardinal Giacomo Antonelli, Secretary of State, that criticized the Mechelen speeches.

[1] Quanta cura was prompted by the September Convention of 1864 between the emerging Kingdom of Italy and the Second French Empire of Napoleon III.

French troops had occupied Rome to prevent the Kingdom of Italy from capturing the city, defeating the Papal States, and completing the unification of the Italian Peninsula under its rule.

In the 1832 encyclical Mirari Vos, Pope Gregory XVI deplored religious indifferentism which"... gives rise to that absurd and erroneous proposition which claims that liberty of conscience must be maintained for everyone.

Experience shows, even from earliest times, that cities renowned for wealth, dominion, and glory perished as a result of this single evil, namely immoderate freedom of opinion, license of free speech, and desire for novelty.

(Hales 1958)[8] John Henry Newman comments on this passage in part 5 of his Letter to the Duke of Norfolk (1874), entitled "Conscience", which precedes part 6, "The Encyclical of 1864"[1]:"And now I shall turn aside for a moment to show {251} how it is that the Popes of our century have been misunderstood by the English people, as if they really were speaking against conscience in the true sense of the word, when in fact they were speaking against it in the various false senses, philosophical or popular, which in this day are put upon the word.

[...] If, under the plea of his revealed prerogatives, he neglected his mission of preaching truth, justice, mercy, and peace, much more if he trampled on the consciences of his subjects,—if he had done so all along, as Protestants say, then he could not have lasted all these many centuries till now, so as to supply a mark for their reprobation.

First, I am using the word "conscience" in the high sense in which I have already explained it,—not as a fancy or an opinion, but as a dutiful obedience to what claims to be a divine voice, speaking within us; and that this is the view properly to be taken of it, I shall not attempt to prove here, but shall assume it as a first principle.

It is the liberty of every one to give public utterance, in every possible shape, by every possible channel, without any let or hindrance from God or man, to all his notions whatsoever [Note 2].

"[9] Regarding the issues of civil control of education, and the separation of church and state, William George McCloskey first rector of the American College at Rome (and later Bishop of Louisville, Kentucky) observed wryly,It is consoling to think that Our Holy Father has in all his official acts a light of guidance from on High, for according to all the rules of mere human prudence and wisdom [Quanta cura] … would be considered ill-timed.