Mormonism vs. Christianity

Few religious boundary disputes generate as much heat as the question of whether Mormonismis Christian. Members of the Church of Jesus Christ of Latter-day Saints (LDS) consider themselves Christian — the name of their church contains the name of Christ, they worship Christ, they read the Bible, and they affirm Christ’s atonement and resurrection. Yet most Catholic, Orthodox, and Protestant theologians classify Mormonism as a distinct religion rather than a Christian denomination. The disagreement is not about semantics; it reflects genuine, fundamental differences in theology, scripture, and the nature of God.

The nature of God: Trinity vs. exaltation

The most profound divergence concerns the nature of God. Mainstream Christianity— Catholic, Orthodox, and Protestant — holds that God is an immaterial, eternal, uncreated spirit: one God in three persons (Father, Son, and Holy Spirit), who has always existed and who created everything else from nothing (creatio ex nihilo).

LDS theology departs from this at every point. God the Father has a physical body of flesh and bone, as Joseph Smith taught: “The Father has a body of flesh and bones as tangible as man’s; the Son also” (Doctrine and Covenants 130:22). The Father, Son, and Holy Ghost are three separate beings united in purpose, not one being in three persons. Most significantly, LDS theology holds that God the Father was once a mortal man who progressed to godhood — and that faithful humans can undergo the same process. “As man now is, God once was; as God now is, man may be,” Lorenzo Snow summarised.

This doctrine of eternal progression, or exaltation, is incompatible with every major Christian creed. The Nicene Creed (“one God, the Father Almighty, maker of heaven and earth”), the Athanasian Creed, and the Westminster Confession all affirm a God who is eternal, unchanging, and ontologically different from creation. A God who was once a man is, from the perspective of traditional Christian theology, not the God of Christianity.

Scripture: the Bible and the Book of Mormon

Christians generally hold that the biblical canon is closed — that the 66 books (Protestant) or 73 books (Catholic) of the Bible constitute the complete written revelation of God. Mormonism adds three additional volumes of scripture: the Book of Mormon (“Another Testament of Jesus Christ”), the Doctrine and Covenants, and the Pearl of Great Price. The Book of Mormon describes Christ’s visit to the Americas after his resurrection and records a history of ancient Israelite peoples in the New World.

For mainstream Christians, the existence of additional scripture is itself disqualifying. If the Bible is the complete word of God, then any addition is either superfluous or heretical. For Latter-day Saints, the Bible has been corrupted over the centuries (“translated correctly” is the qualification in the Articles of Faith), and additional revelation was necessary to restore the truths that had been lost.

The historicity of the Book of Mormon is also a point of contention. Mainstream archaeology, genetics, and linguistics have found no evidence supporting the Book of Mormon’s account of large Hebrew-descended civilizations in pre-Columbian America. LDS scholars have responded with various models (limited geography, spiritual rather than literal interpretation), but the evidentiary gap remains significant.

The apostasy narrative

Mormonism does not position itself as a denomination of Christianity; it claims to be the restoration of original Christianity. According to LDS teaching, shortly after the death of the apostles, the Christian church fell into a “Great Apostasy” — a wholesale corruption of doctrine, authority, and practice. The creeds of the early councils (Nicaea, Chalcedon) were products of this apostasy, not authentic Christian teaching. Joseph Smith’s First Vision and subsequent revelations restored the original church, its priesthood authority, and its correct doctrines.

This is, understandably, difficult for other Christians to accept. The claim is not that Catholicism or Protestantism are imperfect expressions of Christianity; it is that every other Christian tradition has been in apostasy for roughly 1,700 years and that only the LDS Church possesses genuine priesthood authority. This claim is one reason why the relationship between Mormonism and mainstream Christianity is not ecumenical in the way Catholic- Protestant relations have become.

Temple rituals and the afterlife

LDS temple worship has no parallel in mainstream Christianity. Temples (distinct from regular meetinghouses) are where the most sacred ordinances take place: endowments, celestial marriages, and baptisms for the dead. Baptism for the dead — the practice of performing proxy baptisms on behalf of deceased persons who did not accept the gospel in life — is perhaps the most distinctive LDS practice and has no precedent in Christian history outside a brief and obscure mention in 1 Corinthians 15:29.

The LDS afterlife is also structured differently. Rather than the traditional heaven-or-hell binary, Mormon theology describes three degrees of glory: the celestial kingdom (for the most faithful), the terrestrial kingdom (for honourable people who did not accept the fullness of the gospel), and the telestial kingdom (for the wicked who eventually accept Christ). Only a small number end up in “outer darkness.” This is a more generous cosmology than most Christian traditions offer, and it reflects the LDS emphasis on universal opportunity for salvation.

What Latter-day Saints say

It would be unfair to present only the critic’s case. Latter-day Saints argue that the earliest Christians — before Nicaea, before the creeds, before the theological developments of the 3rd and 4th centuries — held beliefs more compatible with LDS theology than with later orthodoxy. They point to New Testament passages that suggest physical divine embodiment, a plurality of divine beings, and an open canon. They argue that defining “Christianity” by the Nicene Creed is a historical choice, not a logical necessity — and that a creed written 300 years after Christ does not have the authority to exclude someone who follows Christ.

The debate ultimately comes down to who gets to define what “Christian” means. If it means “follows Jesus Christ,” Mormons are Christian. If it means “holds to the theological framework codified in the ecumenical creeds,” Mormons are not. Both definitions are defensible. Neither is self-evidently correct.

What an outsider notices

From a secular perspective, the Mormonism-Christianity debate is instructive because it reveals the arbitrariness of religious boundary-drawing. Christianity itself began as a Jewish sect that most Jews rejected as heretical. Islam claims to be the final revelation of the same God that Jews and Christians worship, yet neither accepts it as a continuation of their own tradition. Every religion draws a line between “us” and “not us,” and that line is always contested.

The deeper question, from outside both traditions, is not whether Mormonism is Christian but whether either tradition’s supernatural claims are true. If the resurrection of Jesus is supported by the evidence, then the question of whether Joseph Smith received genuine revelation matters. If the resurrection is not supported by the evidence, then the boundary dispute between Mormonism and mainstream Christianity is a disagreement within a shared framework of faith — and the more fundamental question is whether that framework is warranted in the first place.