1. The Catholic Church justly and truly considers atheism "one of the most serious problems of our time" (CCC 2123) and a grave sin against the first commandment (CCC 2125). Nothing is sadder than to hear some people say they got embroiled in the Catholic-Orthodox theological controversies for years only to later on fall away from Christ altogether, into atheism, agnosticism or some other form of worldliness and impiety.
What do posters here think is the best way for the Church and Christians to answer the objections of atheists and refute the absurdities of atheism and other forms of modernism? Vatican I gave an excellent treatise on the relationship between faith and reason which was incorporated into the Oath against Modernism that all who held teaching offices in the name of the Church were to vow before God to uphold --- "I N. firmly embrace and accept each and every definition that has been set forth and declared by the unerring teaching authority of the Church, especially those principal truths which are directly opposed to the errors of this day. And first of all, I profess that God, the origin and end of all things, can be known with certainty by the natural light of reason from the created world (see Rom. 1:19), that is, from the visible works of creation, as a cause from its effects, and that, therefore, his existence can also be demonstrated: Secondly, I accept and acknowledge the external proofs of revelation, that is, divine acts and especially miracles and prophecies as the surest signs of the divine origin of the Christian religion and I hold that these same proofs are well adapted to the understanding of all eras and all men, even of this time. "(Oath against Modernism, Pope St. Pius X)
2. From Vatican I's decree on faith and reason, "that doctrine of rationalism or naturalism,—utterly opposed to the Christian religion, since this is of supernatural origin,—which spares no effort to bring it about that Christ, who alone is our Lord and Savior, is shut out from the minds of men and the moral life of nations ... The abandonment and rejection of the Christian religion, and the denial of God and his Christ, has plunged the minds of many into the abyss of pantheism, materialism and atheism, and the consequence is that they strive to destroy rational nature itself, to deny any criterion of what is right and just, and to overthrow the very foundations of human society.
With this impiety spreading in every direction, it has come about, alas, that many even among the children of the Catholic Church have strayed from the path of genuine piety ... in order that the submission of our faith should be in accordance with reason, it was God's will that there should be linked to the internal assistance of the Holy Spirit external indications of his revelation, that is to say divine acts, and first and foremost miracles and prophecies, which clearly demonstrating as they do the omnipotence and infinite knowledge of God, are the most certain signs of revelation and are suited to the understanding of all.
... the Church Herself ... by Her Catholic unity and unconquerable stability is a kind of great and perpetual motive of credibility and an incontrovertible evidence of Her own divine mission. So it comes about that, like a standard lifted up for the nations (Isa 11:12), She both invites to Herself those who have not yet believed, and likewise assures Her sons and daughters that the faith they profess rests on the firmest of foundations."