Vatican Council, Session III, Chapter IV (1870):
#6. God cannot deny himself, nor can truth ever be in opposition to truth. The appearance of this kind of specious contradiction is chiefly due to the fact that either the dogmas of faith are not understood and explained in accordance with the mind of the church, or unsound views are mistaken for the conclusions of reason.
#13. For the doctrine of the faith which God has revealed is put forward not as some philosophical discovery capable of being perfected by human intelligence, but as a divine deposit committed to the spouse of Christ to be faithfully protected and infallibly promulgated.
#14. Hence, too, that meaning of the sacred dogmas is ever to be maintained which has once been declared by holy mother church, and there must never be any abandonment of this sense under the pretext or in the name of a more profound understanding.”
Pope St. Simplicius, Cuperem quidem, (476):
“Let whoever, as the Apostle proclaimed, attempts to disseminate something other, than what we have received, be anathema[ Gal. 1:8 f.]. Let no approach to your ears be thrown open to the pernicious plans of undermining, let no pledge of revising any of the old definitions be granted, because, as it must be repeated very often, what has deserved to be cut away with the sharp edge of the evangelical pruning hook by apostolic hands with the approval of the universal Church, cannot acquire the strength for a rebirth nor is it able to return to the fruitful shoot of the master’s vine, because it is evident that it has been destined to eternal fire. Thus, finally, the machinations of all heresies laid down by decrees of the Church are never allowed to renew the struggles of their crushed attack.”
Pope Gregory XVI, Mirari Vos, #7:
“Indeed you will accomplish this perfectly if, as the duty of your office demands, you attend to yourselves and to doctrine and meditate on these words: ‘the universal Church is affected by any and every novelty’ and the admonition of Pope Agatho: ‘nothing of the things appointed ought to be diminished; nothing changed; nothing added; but they must be preserved both as regards expression and meaning.'”
Pope St. Pius X, Lamentabili Sane, Condemned Errors of Modernists(1907):
“With truly lamentable results, our age, casting aside all restraint in its search for the ultimate causes of things, frequently pursues novelties so ardently that it rejects the legacy of the human race. Thus it falls into very serious errors, which are even more serious when they concern sacred authority, the interpretation of Sacred Scripture, and the principal mysteries of Faith. The fact that many Catholic writers also go beyond the limits determined by the Fathers and the Church herself is extremely regrettable. In the name of higher knowledge and historical research (they say), they are looking for that progress of dogmas which is, in reality, nothing but the corruption of dogmas.
Condemned Error #22. The dogmas the Church holds out as revealed are not truths which have fallen from heaven. They are an interpretation of religious facts which the human mind has acquired by laborious effort.
Condemned Error #54. Dogmas, Sacraments and hierarchy, both their notion and reality, are only interpretations and evolutions of the Christian intelligence which have increased and perfected by an external series of additions the little germ latent in the Gospel.”
Catholic Quotes 