To begin answering this question let's be clear that the Roman Catholic Church condems divination, spiritism, and necromancy. In the Catechism of the Catholic Church (CCC) we read:
"All forms of divination are to be rejected: recourse to Satan or demons, conjuring up the dead or other practices falsely supposed to "unveil' the future. Consulting horoscopes, astrology, palm reading, interpretation of omens and lots, the phenomena of clairvoyance, and recourse to mediums all conceal a desire for power over time, history, and, in the last analysis, other human being, as well as a wish to conciliate hidden powers. They contradict the honor, respect, and loving fear that we owe to God alone." (CCC 2116)
The Church teaches that the First Commandment (I am the Lord thy God, thou shall not have strange gods before me) does not forbid us to honor the saints in heaven, provided we do not give them the honor due to God alone (My Catholic Faith, CCC 2116).
So what gives? Is the Church in total contradiction of Herself when She teaches one thing and seemingly in appearances does another? The answer is that the Church is right on both accounts - divination is to be rejected, praying for the intercession of the Saints is to be embraced. The Church makes a clear distinction about who it is Catholics pray to when asking for intercession from the saints. Praying to the saints is really petitioning God's power through an intercessor who likewise subjects himself or herself to God's almighty power (see the
St. Michael Prayer). Divination or necromancy on the other hand, is conjuring souls from the underworld whose influence is from another source. The Catholic understands that any assistance from the saints and angels is from the power of God and God alone, linking this practice to the central belief of Christianity: our hope in the Resurrection to someday be united with our true family in Heaven adoring God alone.
The Church teaches that the veneration we pay to the saints does not in the least detract from the honor due to God, for we only reverence the saints for God's sake. By no means do we reverence them in the way that we reverence God, but only because they are servants of God (The Catechism Explained). The saints have God's image reflected in them. God alone is wonderful in His saints just as the Blessed Virgin Mary proclaims: "He that is mighty hath done great things to me" (Luke 1:49). The goodness the saints possess is a gift from God alone.
When a person dies, they cross from the plane of life into the place of judgment where God will determine, based on the life the person lived, every thought, word, act, and omission, what reward is deserving for the soul. Called the Particular Judgment, "Every one of us will render an account for himself to God" (Romans 14:12). Based on one's account of his whole life, The just will enter into everlasting life (Matthew 25:46) or into hell, "For the hope of the wicked is as dust, which is blown away with the wind . . . and as the remembrance of a guest of one day that passes by" (Wisdom 5:15).
The souls of the wicked have no hope, the souls of the Faithful, by virtue of the hope in the Resurrection, can achieve eternal LIFE beyond the plane of death. Christ's act of the Resurrection is our central hope as Christians. Those wicked souls are gone from memory and hope. Catholics cannot pray to them, nor expect either their salvation or intercession. The Church teaches that we are forbidden to give public veneration to anyone who is not beatified or canonized a saint.
Canonization does not admit any one into heaven; it is only a solemn declaration on the part of the Pope that the man or woman by their holy life and the miracles attributed to the person, is already in Heaven and can therefore be venerated by the Church (The Catechism Explained 1899).
The Catechism of the Catholic Church states:
"By canonizing some of the faithful, i.e., by solemnly proclaiming that they practiced heroic virtue and lived in fidelity to God's grace, the Church recognizes the power of the Spirit of holiness within her and sustains the hope of believers by proposing the saints to them as models and intercessors." (CCC 828)
The Church points to God as the source of holiness, not man. "We know that in everything God works for good with those who love him . . . and those whom he justified he also glorified." (Romans 8:28-80, CCC 2012).
Catholics are often accused of divination because they are not invoking God directly. That God is somehow jealous if we petition someone other than Christ for help. Those who accuse however are refusing to acknowledge the intercessory role every Christian plays for one another by their prayers for them. Anyone can pray for one another, but only God holds the key to answering a prayer. God is not jealous of a person when we ask of them: "Can you pray for me?" It is a charitable thing to pray for another because as Christians we acknowledge that God alone will provide the answer to our prayer.
In 2 Timothy we read: "First of all, then, I urge that
supplications, prayers, intercessions, and thanksgivings be made for all men". St. Paul still on the topic of intercessory prayer then says in 1 Tim 2:3: "This is good and it is acceptable in the sight of God our Savior." St. Paul says this before the verse used by many against Catholics: "For there is one God, one mediator also between God and men, himself man, Christ Jesus" (1 Tim 2:5). What St. Paul is actually saying about Christ Jesus being the one mediator between God and men is Christ is a unique mediator between man and God because he is the only person who is both God and man. He is the only bridge between the two, the only God-man. But that role as mediator is not compromised in the least by the fact that others intercede for us. Furthermore, Christ is a unique mediator between God and man because he is the Mediator of the New Covenant (Heb. 9:15, 12:24), just as Moses was the mediator of the Old Covenant (Gal. 3:19–20). Clearly, then, intercessory prayers offered by Christians on behalf of others is something "good and pleasing to God," not something infringing on Christ’s role as mediator.
St. Luke's Gospel account states:
"And Jesus said unto them, The sons of this world marry, and are given in marriage: but they that are accounted worthy to attain to that world, and the resurrection from the dead, neither marry, nor are given in marriage: for neither can they die any more: for they are equal unto the angels; and are sons of God, being sons of the resurrection. But that the dead are raised, even Moses showed, in the place concerning the Bush, when he calleth the Lord the God of Abraham, and the God of Isaac, and the God of Jacob. Now he is not the God of the dead, but of the living: for all live unto him." Luke 20:34-38
In St. Paul's Letter to the Romans he writes:
"Who shall separate us from the love of Christ? Shall tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword?" (Romans 8:35)
In Romans Ch.8 v.38 St. Paul continues:
"For I am sure that neither death, nor life, nor angels, nor principalities, nor things present, nor things to come, nor powers, nor height, nor depth, nor anything else in all creation, will be able to separate us from the love of God in Christ Jesus our Lord."
The Catechism of the Catholic Church states about the saints experiencing the fullness of life in heaven:
"They contemplate God, praise him and constantly care for those whom they have left on earth. When they entered into the joy of their Master, they were "put in charge of many things."[Mt 25:21] Their intercession is their most exalted service to God's plan. We can and should ask them to intercede for us and for the whole world." (CCC 2683)
Alas, only the Catholic Church, Sacred Scripture's original author and Christ's Representative's on earth by Our Lord's own commissioning, can interpret the Books of the Bible. Only the Apostolic Church upon whom Our Lord Jesus Christ instituted with the power that what they "bind and loose on earth shall be bound and loosed in heaven" (John 20:23; Matthew 16:19, 18:18) can interpret the Bible (and appoint successors). The Church compiled the Bible in the first few centuries of Christianity and using the grace God bestowed upon them, the Church defined, and continues to define, God's revealed truth which He promised to continue teaching to the Church through the Paraclete, the Holy Spirit.
We must also concede that there were no other Christian denominations until the Protestant so called Reformation in the 16th century. Up until then, the Christian denomination was One. It was founded upon the Apostles by Our Lord Jesus Christ who entrusted the Church in their hands to act as His representatives, "Go ye therefore, and make disciples of all the nations, baptizing them into the name of the Father and of the Son and of the Holy Spirit: teaching them to observe all things whatsoever I commanded you: and lo,
I am with you always, even unto the end of the world" (Matthew 28:19-20)
The very last verse of the 4 Gospels ends with this concession:
"And there are also many other things which Jesus did, the which if they should be written every one, I suppose that even the world itself would not contain the books that should be written" (John 21:25).
Our Lord Himself entrusts his teachings not just to the Apostles but to the teaching Church until the end of time:
"Judas saith to him (not the Iscariot): Lord, how is it, that thou wilt manifest thyself to us, and not to the world? Jesus answered, and said to him: If any one love me, he will keep my word, and my Father will love him, and we will come to him, and will make our abode with him. He that loveth me not, keepeth not my words. And the word which you have heard, is not mine; but the Father's who sent me. These things have I spoken to you, abiding with you. But the Paraclete, the Holy Ghost, whom the Father will send in my name, he will teach you all things, and bring all things to your mind, whatsoever I shall have said to you (Matthew 14:22-26).
"But I tell you the truth: it is expedient to you that I go: for if I go not, the Paraclete will not come to you; but if I go, I will send him to you.
". . . I have yet many things to say to you: but you cannot bear them now. But when he, the Spirit of truth, is come, he will teach you all truth. For he shall not speak of himself; but what things soever he shall hear, he shall speak; and the things that are to come, he shall shew you. He shall glorify me; because he shall receive of mine, and shall shew it to you. All things whatsoever the Father hath, are mine." (John 16:7, 12-15)
Thus we have the Church teaching, not all the things which were said by Christ, but
revealed by Christ through the Holy Ghost to His Church which he founded upon the Apostles and will be blessed with Christ's presence until the end of time.
This same Church was the governing figure that put together Sacred Scripture, those written documents composed of Books, Gospels, and Epistles that the Church authoritatively declared as the written word of God, the divinely inspired written Truth.
The canon of both the Old and New Testaments after
centuries of investigation was finally settled in the year 382 at the Council of Rome under Pope Damasus I. It was never challenged until Martin Luther and the Protestant so called Reformers who, acting as their own authority changed the canon of of Scripture to fit their new theology on such things as salvation, faith, and wholesale denial of the sacred priesthood.
Our Heavenly Father, throughout salvation history, gave special authority to men. Abraham, Isaac, Jacob, Judges, Kings, and Prophets represented the Covenant. When Christ came to establish the new Covenant he proclaimed "Think not that I came to destroy the law or the prophets: I came not to destroy, but to fulfill" (Matthew 5:17). He continued to point to the Church as God's guiding light with the Apostles as God's new representatives:
"And if he will not hear them: tell the church. And if he will not hear the church, let him be to thee as the heathen and publican. Amen I say to you, whatsoever you shall bind upon earth, shall be bound also in heaven; and whatsoever you shall loose upon earth, shall be loosed also in heaven" (Matthew 18:17-18).
And so it is that the Apostles with Peter, the first Pope, as their chief Apostle, have lived true to Christ's commission of binding and loosing on earth by defining Church doctrines and passing on their authority until the end of time:
"Jesus saith to them: But whom do you say that I am? Simon Peter answered and said: Thou art Christ, the Son of the living God. And Jesus answering, said to him: Blessed art thou, Simon Bar-Jona: because flesh and blood hath not revealed it to thee, but my Father who is in heaven. And I say to thee: That thou art Peter; and upon this rock I will build my church, and the gates of hell shall not prevail against it. And I will give to thee the keys of the kingdom of heaven. And whatsoever thou shalt bind upon earth, it shall be bound also in heaven: and whatsoever thou shalt loose upon earth, it shall be loosed also in heaven." (Matthew 16:15-19)
"Teaching them to observe all things whatsoever I have commanded you: and behold I am with you all days, even to the consummation of the world" (Matthew 28:20).
Thus, the Church condemns divination which conjures spirits of the dead (CCC 2116). Whereas, in the same authority vested upon Her by Christ Himself, has definitively ascertained certain souls that have entered Eternal Life and declared them saints in Heaven. The formal act of canonizing a saint, is within the Church's revelation by the Holy Spirit, the Paraclete to employ Her God-given authority of binding and loosing.
A man can invest his own money in the market himself directly or through a financial adviser. Without consulting with a financial adviser, who sees the market clearer than we and is in constant contact with the market unlike ourselves, the investor risks making a poor investment that will not bring the returns he desires. A financial adviser then can wisely place our money to provide the best return for our investment. In the same way, the saints can place our petitions before the throne of God all the while submitting to His decision and His almighty power. The saints do not answer our prayers, but rather God does. Compared to the saints in Heaven we have a less clear understanding of how to present our petitions before God because we do not stand before the throne of Him Who we depend on for salvation. However the saints do, and have God's favor as they are standing before His throne. They would therefore wisely present our prayers to God in a more suitable or fitting delivery.
Catholics can venerate the saints, including asking for their intercession. One day we may be united with them in God's Heavenly Kingdom and thus we are united to them, even now, in a mutual love (Romans 8:38). The Catechism Explained tells us that both they and we belong to the same great family whose father is God; petitioning the saints does not betray want of confidence in Christ our great Mediator, but rather distrusting ourselves in that we, unlike the Saints who behold the Beatific Vision, can have recourse to a lesser mediator whose prayers will have greater weight with Him than our own.