In a world where so many cults and false beliefs are going around, it is essential to deepen our Christian Faith, if we don't want to lose it, and fall into Satan's traps.
One of the greatest achievements of John Paul II's pontificate so far is his "Catechism of the Catholic Church" (published in English in 1994), which gives a very clear and solid summary of the Christian Faith. If you want to be a true Catholic, all that you have to follow is in there. Here are excerpts from this Catechism on the first parts of the Apostles' Creed, which summarizes what we must believe:
Scripture and Tradition never cease to teach and celebrate this fundamental truth: "The world was made for the glory of God." St. Bonaventure explains that God created all things "not to increase his glory, but to show it forth and to communicate it", for God has no other reason for creating than his love and goodness: "Creatures came into existence when the key of love opened his hand."
God is the sovereign master of his plan. But to carry it out he also makes use of his creatures' co-operation. This use is not a sign of weakness, but rather a token of almighty God's greatness and goodness. For God grants his creatures not only their existence, but also the dignity of acting on their own, of being causes and principles for each other, and thus of co-operating in the accomplishment of his plan.
Angels and men, as intelligent and free creatures, have to journey toward their ultimate destinies by their free choice and preferential love. They can therefore go astray. Indeed, they have sinned. Thus has moral evil, incommensurably more harmful than physical evil, entered the world. God is in no way, directly or indirectly, the cause of moral evil. He permits it, however, because he respects the freedom of his creatures and, mysteriously, knows how to derive good from it: "For almighty God..., because he is supremely good, would never allow any evil whatsoever to exist in his works if he were not so all-powerful and good as to cause good to emerge from evil itself." (St. Augustine.)
In time we can discover that God in his almighty providence can bring a good from the consequences of an evil, even a moral evil, caused by his creatures: "It was not you", said Joseph to his brothers, "who sent me here, but God... You meant evil against me; but God meant it for good, to bring it about that many people should be kept alive." (Gen 45:8; 50:20.) From the greatest moral evil ever committed - the rejection and murder of God's only Son, caused by the sins of all men - God, by his grace that "abounded all the more", brought the greatest of goods: the glorification of Christ and our redemption. But for all that, evil never becomes a good.
"We know that in everything God works for good for those who love him." (Rom 8:28.) The constant witness of the saints confirms this truth: St. Catherine of Siena said to "those who are scandalized and rebel against what happens to them": "Everything comes from love, all is ordained for the salvation of man, God does nothing without this goal in mind." St. Thomas More; shortly before his martyrdom, consoled his daughter: "Nothing can come but that that God wills. And I make me very sure that whatsoever that be, seem it never so bad in sight, it shall indeed be the best."
The existence of the spiritual, non-corporeal beings that Sacred Scripture usually calls "angels" is a truth of faith. The witness of Scripture is as clear as the unanimity of Tradition. As purely spiritual creatures angels have intelligence and will: they are personal and immortal creatures, surpassing in perfection all visible creatures, as the splendor of their glory bears witness. From its beginning until death, human life is surrounded by their watchful care and intercession. "Beside each believer stands an angel as protector and shepherd leading him to life." (St. Basil.)
Behind the disobedient choice of our first parents lurks a seductive voice, opposed to God, which makes them fall into death out of envy. Scripture and the Church's Tradition see in this being a fallen angel, called "Satan" or the "devil". The Church teaches that Satan was at first a good angel, made by God: "The devil and the other demons were indeed created naturally good by God, but they became evil by their own doing." (Lateran Council IV, 1215.)
The power of Satan is, nonetheless, not infinite. He is only a creature, powerful from the fact that he is pure spirit, but still a creature. He cannot prevent the building up of God's reign. Although Satan may act in the world out of hatred for God and his kingdom in Christ Jesus, and although his action may cause grave injuries - of a spiritual nature and, indirectly, even of a physical nature – to each man and to society, the action is permitted by divine providence which with strength and gentleness guides human and cosmic history. It is a great mystery that providence should permit diabolical activity, but "we know that in everything God works for good with those who love him." (Rom 8:28.)
God created man in his image and established him in his friendship. A spiritual creature, man can live this friendship only in free submission to God. The prohibition against eating "of the tree of the knowledge of good and evil" spells this out: "for in the day that you eat of it, you shall die." (Gen 2:17.) The "tree of the knowledge of good and evil" symbolically evokes the insurmountable limits that man, being a creature, must freely recognize and respect with trust. Man is dependent on his Creator, and subject to the laws of creation and to the moral norms that govern the use of freedom.
Man, tempted by the devil, let his trust in his Creator die in his heart and, abusing his freedom, disobeyed God's command. This is what man's first sin consisted of. All subsequent sin would be disobedience toward God and lack of trust in his goodness.
In that sin man preferred himself to God and by that very act scorned him. He chose himself over and against God, against the requirements of his creaturely status and therefore against his own good. Constituted in a state of holiness, man was destined to be fully "divinized" by God in glory. Seduced by the devil, he wanted to "be like God", but "without God, before God, and not in accordance with God".
Scripture portrays the tragic consequences of this first disobedience. Adam and Eve immediately lose the grace of original holiness. They become afraid of the God of whom they have conceived a distorted image - that of a God jealous of his prerogatives.
The doctrine of original sin, closely connected with that of redemption by Christ, provides lucid discernment of man's situation and activity in the world. By our first parents' sin, the devil has acquired a certain domination over man, even though man remains free. Original sin entails "captivity under the power of him who thenceforth had the power of death, that is, the devil". Ignorance of the fact that man has a wounded nature inclined to evil gives rise to serious errors in the areas of education, politics, social action, and morals.
After his fall, "man was not abandoned by God. On the contrary, God calls him and in a mysterious way heralds the coming victory over evil and his restoration from his fall. (Cf. Gen 3:9, 15.) This passage in Genesis is called the Protoevangelium ("first gospel"): the first announcement of the Messiah and Redeemer, of a battle between the serpent and the Woman, and of the final victory of a descendant of hers.
The Christian tradition sees in this passage an announcement of the "New Adam" who, because he "became obedient unto death, even death on a cross", makes amends superabundantly for the disobedience of Adam. Furthermore many Fathers and Doctors of the Church have seen the woman announced in the Protoevangelium as Mary, the mother of Christ, the "new Eve". Mary benefited first of all and uniquely from Christ's victory over sin: she was preserved from all stain of original sin and by a special grace of God committed no sin of any kind during her whole earthly life.
But why did God not prevent the first man from sinning? St. Leo the Great responds, "Christ's inexpressible grace gave us blessings better than those the demon's envy had taken away." And St. Thomas Aquinas wrote, "There is nothing to prevent human nature's being raised up to something greater, even after sin; God permits evil in order to draw forth some greater good. Thus St. Paul says,'Where sin increased, grace abounded all the more'; and the Exsultet sings: 'O happy fault,... which gained for us so great a Redeemer!""
(And when the time had come, God sent forth His Son Jesus, born of the Virgin Mary, to save us. And He insituted on earth His Church, "one, holy, catholic and apostolic.")