Modernists believe human reason is the guide for determining right and wrong. They want beliefs and morals to conform to current trends
in society and be altered as the need arises. Pope Pius IX describes the tragic results of heresy that are so clearly evident today:
As a result of this filthy medley of errors which creeps in from every side, and as a result of the unbridled license to think, speak and write, we see the following: morals deteriorated, Christ’s most holy religion despised, the majority of divine worship rejected, the power of this Apostolic See plundered, the authority of the Church attacked…the rights of bishops trampled on, the sanctity of marriage infringed, the rule of every government violently shaken…
Pope St. Pius X taught that Modernism attacked every doctrine:
Undoubtedly, were anyone to attempt the task of collecting together all the errors that have been broached against the faith and to concentrate into one the sap and substance of them all, he could not succeed better than the Modernists have done…their system means the destruction not of the Catholic religion alone, but all religion.
Hence the danger is present almost in the very veins and heart of the Church, whose injury is the more certain from the very
fact that their knowledge of Her is more intimate. Moreover, they lay the axe not to the branches and shoots, but to the very root, that is, to the faith and its deepest fibers. And once having struck at this root of immortality, they proceed to diffuse poison through the whole tree, so that there is no part of Catholic truth that they leave untouched, none that they do not strive to corrupt…They distain all authority and brook no restraint.
Three years later he published The Oath Against Modernism and mandated it be taken by all seminarians before ordination to Major Orders, by professors of philosophy and theology in seminaries and universities, and by confessors, pastors, preachers and religious
superiors.
Pope Benedict XV in the encyclical Ad beatissimi Apostolorum of November 1, 1914, warned of “the monstrous errors of Modernism.”
Pope Pius XI in his encyclical Mortalium Animos taught that Christ’s teachings are not to be updated in each age, but rather are to remain
intact and preserved unchanged.
Pope Pius XII said Modernists interpret Scripture by human reason, rejecting the Church, who alone has authority from Christ to correctly
interpret Divine Revelation.