Hundreds of Catholics each year are led to doubt their faith because they do not know the biblical basis of it. What is the biblical basis of our faith? Why are we Catholic?
The first reason to be Catholic is Jesus Christ.
Who Was/Is Jesus Christ?
Jesus of Nazareth is the only founder of a religion who was pre-announced hundreds of years before his birth. In Isaiah 53, written several centuries before Christ, we read:
(v5)...he was pierced for our offenses, crushed for our sins, Upon him was the chastisement that makes us whole, by his stripes we were healed.
(v12)...Therefore I will give him his portion among the great, and he shall divide the spoils with the mighty, Because he surrendered himself to death and was counted among the wicked; And he shall take away the sins of many, and win pardon for their offenses.
Also, see Is 49:1-7; 50:4-11; and the rest of Is 53.
In Psalm 22, written as early as 980 BC, we find what could pass for an eye-witness account of the crucifixion of Jesus (the opening words of which he quotes in Mt 27:46).
My God, my God, why have you forsaken me... All who see me scoff at me... "He relied on the Lord; let him deliver him..." They have pierced my hands and my feet; I can count all my bones... They divide my garments among them; for my clothing they cast lots...
Also, Jesus is the only person ever to predict and carry out his own rising from the dead. But, could the apostles have fabricated the resurrection? Not likely. The apostles, who were clearly hard-nosed skeptics would hardly have endured martyrdom one by one---all but John died as martyrs---for a religion founded on a hoax.
So, clearly, Jesus was sent by God. But, was there more to him than that? Infinitely more. He said in the clearest Semitic way (i.e., indirectly) that he was God. In Mk 2:5 he forgave sins on his own authority. The Jews knew well what he was saying by this and responded, "He commits blasphemy! Who can forgive sins but God alone?"
In Jn 8:58 Jesus said, "Before Abraham came to be I AM." This "I AM" is the same name God used for himself when he sent Moses to the Israelites to say: "I AM sent me to you" (Ex 3:14). So Jesus was not only saying he pre-existed, even before Abraham who lived almost 2,000 years prior to him; he was also saying by a play on words that he, Jesus, was "I AM," or God. Again, the Jews knew well what Jesus was saying; they picked up rocks to throw at him (Jn 8:59). Stoning (Lv 24:16) was the penalty for such blasphemy.
Finally, in Jn 10:30 Jesus said, "The Father and I are one." Again, upon hearing this the Jews reached for rocks to stone him saying, "You who are only a man are making yourself out to be God."
In none of these three cases did Jesus avoid trouble by telling them he did not mean to say he was God. He knew very well what he was saying, and so did the Jews.
But, you might ask, what about passages such as "The Father is greater than I" (Jn 14:28), and regarding the end time, no one, not even the son knows the day and the hour, "but only the Father" (Mk 13:32), and in Gethsemane, praying to the Father, "not my will but yours be done" (Lk 22:42)? All of these quotes merely point to the human nature of Christ which was united to his divine nature. Had he not said these things, his human nature might have been doubted by the references to his divinity. (All of this was debated and sorted out by the early Church: Christ's divinity was defined in 325, his two natures, in 451 AD.)
So, either Jesus was divine, as he said clearly enough that the Jews accused him of blasphemy, or he was crazy, totally deranged. Either he was all he said he was, or he was nothing.
Now, what about the Catholic Church? Is it true to Christ and His Sacred Scriptures?
The Real Presence in the Eucharist
First, consider the Eucharist. Christ said:
I myself am the living bread come down from heaven. If anyone eats this bread he shall live forever; the bread I will give is my flesh for the life of the world (Jn 6:51).
When the Jews balked at this he went on (v 53):
Let me solemnly assure you, if you do not eat the flesh of the Son of Man and drink his blood, you have no life in you... for my flesh is real food, and my blood real drink (6:55).
This really set them off, since drinking blood was unthinkable to a Jew. To even touch blood required ritual purification. All Jesus had to say here to eliminate their fears was, "No, no, no. This is merely a symbol!" but he didn't. He said:
Does it shake your faith? ...What then if you were to see the Son of Man ascend to where he was before...? (Jn 6:61, 62)
What was the result of all this? Many of his disciples left him (Jn 6:66).
Now we must ask, would Jesus have given up "many" of his disciples for a "symbol" of his body and blood? This hardly seems likely. No, he knew that what he was going to institute, namely the Eucharist, was going to require a radically new way of thinking for his followers.
But, what about Jn 6:63?:
It is the spirit that gives life; the flesh is useless. The words I spoke to you are spirit and life.
Doesn't this imply merely a symbol? Not at all. It simply means that Jesus was speaking of something which would not be visible by the physical eyes of the flesh (thus allaying any accusation of cannibalism), but only spiritually, by faith.
So, the Catholic Church is being faithful to the Scriptures in believing in the real presence of Christ in the Eucharist. It's radical, but fully biblical.
The Holy Sacrifice of the Mass
Consider next the Mass. Catholics (and the Orthodox) hold the Mass to be, "above all else a sacrifice" (Pope John Paul II, 2/24/80).
In Mt 26:26-28 Jesus said of the bread at the Last Supper, "Take this and eat... This is my body..." and of the cup, "Drink of it, all of you; for this is my blood, the blood of the covenant, to be shed for many for the forgiveness of sins." Giving one's body and shedding one's blood for the forgiveness of sins are biblical expressions which speak of a true sacrifice. It is this divine, timeless sacrifice of Jesus' death which we "re-present" in the Mass: "his body and blood are both really present; the species under which he is present symbolize the actual separation of his body and blood... on Calvary" (Pius XII, Mediator Dei, 11/20/47).
Also, in Psalm 110, clearly referring to the Messiah, Christ is called a priest according to the order of Melchizedek (see Heb 5:5-10 as well). Melchizedek (Gen 14:18) offered bread and wine as a sacrifice to God for a victory celebration. Christ offers his body and blood under the appearance of bread and wine as a sacrifice to God.
Finally, in Mal 1:10,11 the prophet predicts that everywhere the Gentiles will bring incense and a pure "food-offering" for God. The only "pure" offering sacrificed "everywhere" in this, the "Messianic Age," is the body and blood of Christ at Mass.
Jesus said to his disciples whom he sent forth in Jn 20:23, "Whose sins you shall forgive they are forgiven; whose sins you shall retain they are retained." The Catholic Church fulfills this by both forgiving and retaining sins (depending on the case) in the sacrament of Penance. It would be impossible to "retain" sins if the penitent's disposition were not known to the priest, acting in the name of Christ.
In Mt 16:18, 19 Jesus said to Peter, "You are 'Rock,' and on this rock I will build my church, and the powers of Hell shall not prevail against it. I will give you the keys of the Kingdom of Heaven. Whatever you bind on earth shall be bound in Heaven; whatever you loose on earth shall be loosed in Heaven." Catholics believe that Jesus gave these powers not personally, to end with Peter's death (hardly worth mentioning if he did) but in his office as leader of his church. Peter's church leadership was also established in Jn 21:15-17. Did Christ intend the Church to be leaderless, and without a source of doctrinal unity, without even an authority to establish which books belong in the New Testament (the Catholic Church did just this from the 4th century onward)? Not likely.
Thus, in claiming the successor of Peter as its leader, and central source of doctrinal authority, the Catholic Church is being faithful to Scripture.
Christ said in Mt 7:17, 20 "Every sound tree bears good fruit... Therefore from their fruits you shall know them." The "fruits" of the Catholic faith are the saints. Has any other religion besides our own been able to produce the likes of St Francis of Assisi, St Teresa of Avila, St John Vianney or St Thérèse of Lisieux? (Read their stories: they will amaze you!) And, if Jeremiah and Onias were, after having died, able to pray for their people (2 Mac 15:11-16), and the saints offered "the prayers of God's holy people" before God (Rv 5:8), does it not make sense for us to seek the saints' intercession?
Mary, Mother of God
There can be no doubt that Jesus lived perfectly the fourth commandment: Honor your father and mother. If Christ lives in us as he did in Paul (Gal 2:20) ought not we venerate Christ's mother as he did, especially since veneration was offered to angels in Josh 5:14 and Dan 8:17? How much greater than the angels is Mary! The Catholic Church honors Mary in imitation of her Son.
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Granted, of course, the Catholic Church has had its scandals, as has every church, but these are the wounds in the body of Christ, put there by the sins of mankind. How wondrous, that despite these wounds, the Church has continued on, and has produced saints in every age.
So, why embrace Catholicism? Because it was founded by the Son of God, it has the Eucharist, and it is eminently biblical. Don't let anyone convince you otherwise!