Finishing up our look at how Mormonism and Roman Catholicism are, basically, theological cousins. Maybe not first cousins, more like third cousins twice removed. But they both spring from the same tree, and they both have the same father (small-'f').
They both teach that the blood of Christ is not the only way to pay for our sins
--Catholicism teaches that the person must pay for some sins themselves in Purgatory.
Catechism of the Catholic Church (CCC), paragraphs 1030-1031--1030 All who die in God's grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven. 1031 The Church gives the name Purgatory to this final purification of the elect, which is entirely different from the punishment of the damned. The Church formulated her doctrine of faith on Purgatory especially at the Councils of Florence and Trent...we understand that certain offenses can be forgiven in this age, but certain others in the age to come."
--Mormonism teaches forgiveness beyond the grave
Gospel Principles (GP), 1997 ed., chapter 45, p. 292-293--"In the spirit prison are the spirits of those who have not yet received the gospel of Jesus Christ. These spirits have agency and may be enticed by both good and evil. If they accept the gospel and the ordinances performed for them in the temples, they may prepare themselves to leave the spirit prison and dwell in paradise. Also in the spirit prison are those who rejected the gospel after it was preached to them on earth or in the spirit prison...After suffering in full for their sins, they will be allowed to inherit the lowest degree of glory, which is the telestial kingdom."
--Early Mormon leaders also taught the doctrine of "Blood Atonement", which means that a person can commit a sin that can only be forgiven by them shedding their own blood. (PSSTT--Remember last week, we saw that in the Mormon church and the Roman Catholic church there are things that aren't "official doctrine" even though they are taught over and over and over again? This is one of them!)
Brigham Young, Journal of Discourses Volume 3 Page 247 (1856)--"Suppose you found your brother in bed with your wife, and put a javelin through both of them, you would be justified, and they would atone for their sins and be received into the kingdom of God."
Joseph Fielding Smith, Doctrines of Salvation, Volume 1 Page 133--"But man may commit certain grievous sins...that will place him beyond the reach of the atoning blood of Christ. If then he would be saved he must make sacrifice of his own life to atone—so far as in his power lies—for that sin, for the blood of Christ alone under certain circumstances will not avail."
Bruce R. McConkie, Mormon Doctrine, Pages 92-93, 1966 edition--"But under certain circumstances there are some serious sins for which the cleansing of Christ does not [pay for], and the law of God is that men then have their own blood shed to atone for their sins."
You can read more words of Mormon leaders on "Blood Atonement" here.
They both teach that one must honor their leader
--Catholicism teaches that one must honor the Pope.
CCC, paragraph 882, 889--"For the Roman Pontiff, by reason of his office as Vicar of Christ, and as pastor of the entire Church has full, supreme, and universal power over the whole Church, a power which he can always exercise unhindered...the People of God, under the guidance of the Church's living magisterium, unfailingly adheres to this faith."
Pope Boniface VIII, Unam Sanctam, 468, [quoted in Apostolic Digest, by Michael Malone, Book 4, Chapter 4]--"If, therefore, the Greeks or others say that they are not committed to Peter and to his successors, they necessarily say that they are not of the sheep of Christ, since the Lord says that there is only one fold and one shepherd (Jn.10:16). Whoever, therefore, resists this authority, resists the command of God Himself."
Dogmatic Constitution on the Church of Christ July 18, 1870 Chapter 3--"[I]f anyone says that the Roman pontiff has merely an office of supervision and guidance, and not the full and supreme power of jurisdiction over the whole church...or that this power of his is not ordinary and immediate both over all and each of the churches and over all and each of the pastors and faithful let him he anathema."
Pope Leo XIII, Acts of Leo XIII, Satis Cognitum, Rome, Vatican Press, 1896--"[T]hose who refuse to associate in communion with the Chair of Peter belong to Antichrist, not to Christ. He who would separate himself from the Roman Pontiff has no further bond with Christ."
Fifth Lateran Council, session 11, On the abrogation of the Pragmatic Sanction, December 19, 1516--"[S]ubjection to the Roman pontiff is necessary for salvation for all Christ's faithful..."
Pope Pius XI Papal Teachings – The Church, Mystici Corporis, St Paul Editions 1962 para 1040-1041--"To be Christian, one must be Roman, governed by Christ's Vicar on earth. The Church does not rest on Christ alone, but also on Peter. That Christ and His Vicar constitute only one single Head is solemn teaching. Therefore, those who think they can accept Christ as the Head of the Church without adhering faithfully to His Vicar on earth are in dangerous error."
To read more about the Roman Catholic teaching that if one does not honor the Pope they are Anathema, see here.
--Mormonism teaches that one must honor Joseph Smith in the same way they honor Christ.
Brigham Young, Journal of Discourses (7:289)--"From the day that the Priesthood was taken from the earth to the winding-up scene of all things, every man and woman must have the certificate of Joseph Smith, junior, as a passport to their entrance into the mansion where God and Christ are--I with you and you with me. I cannot go there without his consent."
1988 Melchizedek Priesthood Study Guide, p.142--"If we get our salvation, we shall have to pass by him [Joseph Smith]; if we enter our glory, it will be through the authority he has received. We cannot get around him [Joseph Smith]."
Joseph Fielding Smith, Doctrines of Salvation, vol. 1, p.190--"[There is] no salvation without accepting Joseph Smith. If Joseph Smith was verily a prophet, and if he told the truth...no man can reject that testimony without incurring the most dreadful consequences, for he cannot enter the kingdom of God."
Joseph F. Smith, Gospel Doctrine, 5th ed., p.134; quoted in “Joseph Smith: Restorer of Truth,” Ensign, Dec 2003, 17--“The day will come – and it is not far distance, either – when the name of the Prophet Joseph Smith will be coupled with the name of Jesus Christ of Nazareth…”
James E. Faust, “Joseph Smith and the Book of Mormon,” Ensign, Jan 1996, p. 2--"A person will never be truly on the road to conversion until he has at least a beginning witness that Joseph Smith was a prophet of God and that the Book of Mormon is another testament of Christ. Further, members of this Church must accept, and its missionaries must teach, some absolutes. These absolutes are: (1) That Jesus is the Christ, the Savior and the Redeemer of all mankind through his atonement; (2) That through Joseph Smith, a prophet of God, the gospel of Jesus Christ was restored in its fulness."
A. Theodore Tuttle, Joseph Smith re-established fullness of true gospel, Church, Church News, March 17, 2001, p.14--"Every man who has lived since the days of Joseph Smith is subject to accepting him as a prophet of God in order to enter into our Heavenly father’s presence."
They both teach that their leader (Pope, Prophet/President) is still giving new, authoritative revelations today.
--The Catholic Pope speaks ex cathedra
CCC, paragraph 891--"The Roman Pontiff, head of the college of bishops, enjoys this infallibility in virtue of his office, when, as supreme pastor and teacher of all the faithful - who confirms his brethren in the faith he proclaims by a definitive act a doctrine pertaining to faith or morals...'The infallibility promised to the Church is also present in the body of bishops when, together with Peter's successor, they exercise the supreme Magisterium', above all in an Ecumenical Council. When the Church through its supreme Magisterium proposes a doctrine "for belief as being divinely revealed," and as the teaching of Christ, the definitions "must be adhered to with the obedience of faith." This infallibility extends as far as the deposit of divine Revelation itself."
Vatican I, Session 4, chapter 4, paragraph 9--"Therefore, faithfully adhering to the tradition received from the beginning of the Christian religion, for the glory of God our Savior, for the exaltation of the Catholic faith and the salvation of the Christian people, with the approval of the sacred council, we teach and define that it is a divinely revealed dogma that the Roman Pontiff, when he speaks "ex cathedra," i.e., when exercising his office as pastor and teacher of all Christians he defines, by his supreme apostolic authority, a doctrine of faith or morals which must be held by the universal Church, enjoys, through the divine assistance, that infallibility promised to him in blessed Peter...So then, should anyone have the temerity to reject this definition of ours: let him be anathema."
--Mormonism teaches strict adherence to the word of the Prophet/President
Doctrine and Covenants (D&C) 132:54--"And I command mine handmaid, Emma Smith, to abide and cleave unto my servant Joseph, and to none else. But if she will not abide this commandment she shall be destroyed, saith the Lord; for I am the Lord thy God, and will destroy her if she abide not in my law."
Elaine Cannon, If We Want to Go Up, We Have to Get On, Ensign, Nov 1978, p.107--"Personal opinions may vary. Eternal principles never do. When the prophet speaks, sisters, the debate is over."
Elder Eldon Tanner references this quote in an later article (N. Eldon Tanner, 'The Debate Is Over', Ensign, Aug 1979, p.2)--Recently, at the Churchwide fireside meeting held for the women of the Church, Young Women President Elaine Cannon made the following statement: "When the Prophet speaks, sisters, the debate is over." I was impressed by that simple statement, which carries such deep spiritual meaning for all of us. Wherever I go, my message to the people is: Follow the prophet."
President Henry D. Moyle, “Beware of Temptation,” as quoted in Teachings of the Living Prophets, Religion 333 Student Manual, p. 19--“The older I get and the closer the contact I have with the President of the church, the more I realize that the greatest of all scriptures which we have in the world today is current scripture. What the mouthpiece of god says to His children is scripture. It is intended for all the children of god upon the earth. It is His word and His will and His law made manifest through His ordained and anointed servant to the world. What the President says is scripture, and I love it more than all other. It applies to me today specifically, and to you all.”
Teachings of the Living Prophets: Religion 333 Student Manual, p. 20--"Occasionally misinformed members of the Church will maintain that, although they accept the standard works as divinely inspired, they are reluctant to give equal credence to pronouncements of the living prophet. Such individuals are pursuing an inconsistent course and 'err, not knowing the scriptures' (Matthew 22:29), for the scriptures themselves plainly testify of the fact that we must give heed to the living prophets (see D&C 1:14, 38; 21:1, 4-5)."
For more quotes concerning the need to follow the living "Prophet" see here.
So, in conclusion, we see that--
Catholics believe that indulgences can be made for the dead. Mormons believe that one can be baptized for the dead.
Catholics believe that the Pope and the Magisterium hold the "Keys of the Kingdom" and speak for God. Mormons believe their Prophet/President holds the "Keys of the Priesthood" and speaks for God.
Catholics believe that the Bible alone is not sufficiently authoritative--you need the Bible AND Tradition AND the Catechism to know the truth. Mormons believe that the Bible alone is not sufficiently authoritative--you need the Bible (so far as it is correctly translated) AND the Book of Mormon AND the Doctrine and Covenants AND the Pearl of Great Price AND the words of the living "Prophet" to know the truth.
Catholics believe we are saved by grace AND "good works". Mormons believe we are saved by grace "after all that we can do."
Catholics believe their church alone is the continuation of the church founded by Christ. Mormons believe that their church alone has restored the church founded by Christ.
Catholics believe wrongly about Mary (that she was born sinless, that we must believe rightly about her to be saved). Mormons believe wrongly about Mary (that she was impregnated by God the Father).
Catholics and Mormons both believe that some sins cannot be paid for by the blood of Christ, but may be (or may need to be) paid for by the person themselves (or by someone else on their behalf) after they die.
Catholics believe that if one does not honor the Pope properly, they are not saved. Mormons believe that if one does not honor Joseph Smith (as well as the living "Prophet") properly, they may not be saved.
Catholics believe that one must dogmatically accept the teachings of the Pope. Mormons believe that one must dogmatically accept the teachings of the living "Prophet."
So, as you can see, as much as the early Mormon leaders decried the Romish church, they have more in common with Rome than they do with (small-'o') orthodox Christianity. And hopefully you can see, now, how deeply the roots of Mormonism and Catholicism are intertwined. After all, they grow from the same family tree.