Defending The Purity of Christian Doctrine and What is Fundamentally Christian

The purpose of this paper is to scrutinize the doctrinal and fundamental truths of Christianity in order to preserve the integrity of the faith by clearly defining the objective truths that form its foundation. It aims to articulate the essential beliefs that are consistent with the teachings of Jesus Christ, who is the perfect fulfillment of Scripture. By systematically dissecting such fundamental doctrines, this paper will distinguish between what is authentically Christian and what deviates from the revealed truth. The ultimate goal is to defend and uphold the core tenets of Christianity as they have been faithfully received and preserved since the time of Jesus and the apostles, thereby protecting the doctrinal integrity of the Christian faith.

Statement of Doctrine

Christianity is the belief that Jesus Christ is the Lord and God of the universe. He is one with the Father and the Holy Spirit, not merely symbolically, but truly consubstantial, one being in three distinct Persons. He is the eternal Son of God, who, according to the will of the Father, was conceived by the Holy Spirit and born of the Blessed Virgin Mary, taking on human nature for the salvation of humanity. In perfect fulfillment of the Scriptures, Jesus Christ was crucified under Pontius Pilate, offering Himself as the once and for all sacrifice acceptable to the Father. Through His Passion, death, and Resurrection, He reconciled humanity to God, opening the way to eternal life. This central truth is the foundation of the Christian faith, rooted in divine revelation and upheld by Sacred Scripture and the testimony of the earliest Christian community. These are the essential beliefs of Christianity: the triune nature of God, the Incarnation and Virgin Birth of Christ, His atoning death on the cross, His bodily Resurrection, His Ascension into Heaven, and His promised return to judge the living and the dead.

Christians also affirm the divine inspiration and authority of Sacred Scripture as the revealed Word of God. Where these foundational truths are upheld, there is true faith in Jesus Christ, and communion with Him is possible. Even when ecclesial communion is lacking due to doctrinal or institutional separation, those who hold to these core truths remain brothers and sisters in Christ by virtue of their faith in the one true Lord (Catechism of the Catholic Church, 1997, paragraphs 818–819; English Standard Version Bible, 2001, Ephesians 4:4–6). This is why the question of faithful Christianity cannot be separated from the question of doctrinal continuity, because Christianity is not merely a label, but a revealed faith that has content, boundaries, and an objective identity preserved through time.

Church History

From its very beginning, Christianity was not a vague spiritual movement or a fragmented collection of personal interpretations. It was a visible, unified, and sacramental community founded directly by Jesus Christ. The Church He established was already Catholic in essence, not as a denominational label, but in the truest and most ancient sense of the word.

The term Catholic comes from the Greek word katholikos, meaning “according to the whole” or “universal.” It described the Church’s mission to proclaim the Gospel in its entirety to all peoples, in every place and time. This universality was also a mark of internal unity in belief and worship. Christ Himself prayed for this unity in His High Priestly Prayer: “that they may all be one, just as you, Father, are in me, and I in you” (John 17:21, ESV).

The Catholic Church is not something separate from the Church Christ founded, but the historical continuation of it. Saint Ignatius of Antioch, a direct disciple of the Apostle John, first referred to the Church as “Catholic” in the early second century. In his Letter to the Smyrnaeans (8:2), he wrote, “Wherever the bishop appears, there let the people be; as wherever Jesus Christ is, there is the Catholic Church.” This was not a title of later invention or exclusion but a descriptor of the Church’s true identity: united, apostolic, and universal.

Ignatius also affirmed the Church’s sacramental character, especially the reality of the Eucharist, which he described as “the flesh of our Savior Jesus Christ” (Smyrnaeans 7:1), clearly opposing those who denied the real presence.

The integrity and unity of Christian doctrine in the early Church were safeguarded through apostolic succession and the discernment of the Holy Spirit. Nowhere is this more evident than in the compilation of the New Testament. Contrary to some popular misconceptions, the Bible was not handed down fully formed in the first century. Rather, it was through the careful discernment of the Catholic bishops, under the guidance of the Holy Spirit, that the canon of Scripture was recognized. The Councils of Hippo (393 AD) and Carthage (397 AD) affirmed the 27 books of the New Testament that are accepted to this day. As Bruce L. Shelley writes in Church History in Plain Language, “The church did not create the canon, but it recognized, collected, and preserved the books inspired by God” (Shelley, 2013, p. 67). These texts were included based on apostolic origin, theological consistency, and widespread liturgical use.

Over time, some ecclesial communities separated from the Church’s structure. The most historically significant among them are the Eastern Orthodox Churches. Their separation from Rome, often dated to the Great Schism of 1054, arose primarily from disputes over papal authority and the addition of the Filioque clause (“and the Son”) to the Nicene Creed. Despite this division, the Orthodox Churches have preserved valid apostolic succession, the sacraments, and a shared faith in the teachings of the early Church. They remain deeply rooted in the apostolic tradition and are doctrinally closer to Catholicism than any other Christian body.

Other communities, particularly those within Protestantism, vary widely in doctrine and ecclesial structure. Many of these preserve essential Christian doctrines such as the Trinity, the divinity of Christ, the authority of Scripture, and the salvific nature of His death and Resurrection. While not united in sacramental theology or hierarchical structure, these communities often maintain a sincere commitment to the core message of the Gospel and a deep reverence for Christ.

However, some groups diverge so significantly from foundational Christian teachings that they no longer fit within the bounds of Christian orthodoxy, despite using the name of Christ. For example, the Church of Jesus Christ of Latter-day Saints (Mormons) teaches that God the Father was once a man who became divine and that human beings may also become gods through a process called exaltation. This belief is directly stated in Doctrine and Covenants 132:20: “Then shall they be gods, because they have no end... then shall they be above all, because all things are subject unto them” (The Church of Jesus Christ of Latter-day Saints, 2013). This view stands in direct contradiction to the Christian understanding of God as the uncreated, eternal, and singular Divine Being. Jehovah’s Witnesses likewise deny the divinity of Christ and the doctrine of the Trinity, rejecting essential components of Christian doctrine.

As established earlier, authentic Christianity is not merely belief in the name of Jesus but adherence to the truths He revealed and the foundation laid by the apostles. At the same time, it is vital to approach these theological issues with humility and charity. The Church has always distinguished between judging doctrines and judging souls. Pope Francis has clearly stated that “the Church cannot condemn anyone to hell. We must leave this to the mercy of God.” The Catechism echoes this: “Although we can judge that an act is gravely sinful, we must entrust judgment of persons to the justice and mercy of God” (Catechism of the Catholic Church, 1997, paragraph 1861). Jesus Himself declared, “Whoever confesses that Jesus is Lord shall not perish but have eternal life” (cf. Romans 10:9; John 3:16). While grave errors can lead people away from truth and impair spiritual life, it is not within our power to make absolute declarations regarding anyone’s eternal destiny. That belongs to God alone.

The Christian faith, historically and doctrinally, is rooted in the Church that Christ established through the apostles. This Church has remained visible, apostolic, and united from the first century onward. Understanding Church history is not about claiming superiority but about recognizing continuity: the enduring presence of the Church Christ founded and the call for all believers to remain faithful to the truth He revealed. This continuity is not merely historical. It is doctrinal, because faithful Christianity depends upon identifiable truths that have always defined Christianity and still define it now.

Defining Doctrine

To understand what makes a belief system authentically Christian, one must begin with the shared foundation that unites the broadest traditions of the Christian faith. Despite differences in structure, liturgy, or secondary doctrines, there are several fundamental beliefs universally affirmed by the Catholic Church, the Eastern Orthodox Churches, and the majority of Protestant denominations. These doctrines form the bedrock of the Christian faith and are considered non-negotiable for any community that professes to follow Jesus Christ as Lord and Savior. These core Christian doctrines include:

The Trinity: One God in three Persons, Father, Son, and Holy Spirit, coequal and coeternal. This mystery of divine unity within distinction is foundational to Christian theology and clearly attested in both Scripture and the early creeds.

The Incarnation: Jesus Christ is fully God and fully man, conceived by the Holy Spirit, born of the Virgin Mary, and united in one divine Person without confusion or separation of His two natures.

The Atonement and Resurrection: Christ’s death on the cross was a real, historical event that brought about the atonement for sin. His bodily Resurrection from the dead is a definitive affirmation of His divinity and the promise of eternal life.

The Ascension and Second Coming: Jesus ascended into heaven and sits at the right hand of the Father. He will return in glory to judge the living and the dead, bringing the fullness of His Kingdom.

Salvation by Grace through Faith: While traditions differ on how grace is dispensed (e.g., sacraments, sola fide), all orthodox Christian traditions affirm that salvation is a gift of God’s grace, made possible through Christ’s sacrifice and accessed by genuine faith.

The Authority of Scripture: The Bible is the inspired Word of God, trustworthy for teaching, reproof, correction, and training in righteousness (2 Timothy 3:16). While interpretations vary, the authority of Scripture is central to all historic Christian communities.

Adherence to the Creeds: The Nicene Creed, formulated in 325 AD and affirmed across all apostolic Churches, serves as a touchstone of orthodoxy. Its confession of belief in one God, one Lord Jesus Christ, the Holy Spirit, and one holy, catholic, and apostolic Church provides a doctrinal standard by which Christian faith is measured.

These doctrines unite the global Christian community and serve as the necessary criteria for determining whether a movement or teaching can rightly be considered part of the Christian faith. When these essentials are upheld, communion in Christ remains possible, even when ecclesial or sacramental divisions exist. These doctrines are most clearly and authoritatively expressed in the Nicene Creed, the universal profession of faith adopted by the Church at the First Council of Nicaea (325 AD) and expanded at the First Council of Constantinople (381 AD). It remains a central statement of Christian orthodoxy across Catholic, Orthodox, and most Protestant traditions:

The Nicene Creed (381 AD)

I believe in one God, the Father almighty,

maker of heaven and earth,

of all things visible and invisible.

I believe in one Lord Jesus Christ,

the Only Begotten Son of God,

born of the Father before all ages.

God from God, Light from Light,

true God from true God,

begotten, not made,

consubstantial with the Father;

through Him all things were made.

For us men and for our salvation He came down from heaven,

and by the Holy Spirit was incarnate of the Virgin Mary,

and became man.

For our sake He was crucified under Pontius Pilate,

He suffered death and was buried,

and rose again on the third day

in accordance with the Scriptures.

He ascended into heaven

and is seated at the right hand of the Father.

He will come again in glory

to judge the living and the dead

and His kingdom will have no end.

I believe in the Holy Spirit,

the Lord, the giver of life,

who proceeds from the Father and the Son,

who with the Father and the Son is adored and glorified,

who has spoken through the prophets.

I believe in one, holy, catholic, and apostolic Church.

I confess one Baptism

for the forgiveness of sins

and I look forward to the resurrection of the dead

and the life of the world to come. Amen.

(Council of Nicaea & Council of Constantinople, 381)

Because these doctrines are definable, they can be defended, and because they can be defended, boundaries can be drawn where a belief system alters them in substance.

Defense of Christian Doctrine

Defending christian doctrine is a matter of faithfulness to the truth entrusted to the Church by Christ. Scripture calls believers to "contend for the faith that was once for all delivered to the saints" (Jude 1:3, ESV), implying that the faith is not merely experiential but contains objective, definable truths. These truths were not invented by men but revealed by God, passed down through apostolic teaching, and preserved through sacred tradition and Scripture. Throughout history, the Church has discerned between central doctrines that define Christianity and secondary issues that allow for diversity within unity. The defining doctrines include belief in one God in three Persons, the Incarnation of Jesus Christ, His atoning death, bodily Resurrection, and future return.

These truths have been consistently affirmed in the creeds, especially the Nicene Creed, and are the basis of communion among Christian communities, even when ecclesial structures differ. A belief system ceases to be Christian when it alters these central tenets in substance. This is not a matter of sincerity or cultural identity but of doctrinal integrity. For instance, belief in Jesus Christ must align with the apostolic witness of who He is: the eternally begotten Son of God, consubstantial with the Father, and the only means of salvation. Redefining Jesus as a created being or denying the Trinity constitutes a fundamental departure. Clarifying these boundaries is not an act of exclusion but of charity. To blur the lines between truth and error risks misleading others. As Jesus prayed, "Sanctify them in the truth; your word is truth" (John 17:17, ESV). The Church is called to bear witness to this truth with both courage and humility. Doctrinal defense also requires discernment. It is the responsibility of the Church to judge teachings, not to condemn individuals. As the Catechism states, “Although we can judge that an act is gravely sinful, we must entrust judgment of persons to the justice and mercy of God” (Catechism of the Catholic Church, 1997, para. 1861). Pope Francis echoes this principle, reminding believers that only God knows the heart.

In sum, the defense of doctrine is a necessary expression of fidelity to Christ. It preserves the Gospel, protects the faithful, and invites all people into communion with the living God. Christianity is not a flexible label for well meaning spirituality; it is a revealed faith grounded in historical truth, theological precision, and the person of Jesus Christ, who is “the same yesterday and today and forever” (Hebrews 13:8). This requires that doctrinal departures be named plainly when they redefine the core truths of Christianity.

Doctrinal Departures

The Church of Jesus Christ of Latter-day Saints (LDS), commonly referred to as the Mormon Church, makes frequent use of Christian vocabulary and professes belief in Jesus Christ. However, its theological framework departs so significantly from the essential doctrines of historic Christianity that it cannot be considered part of the Christian faith as defined by Scripture, the early creeds, and apostolic tradition.

Rejection of the Trinity

The LDS Church denies the doctrine of the Trinity, teaching instead that the Father, Son, and Holy Ghost are three distinct gods, united in purpose but separate in substance. This directly contradicts the Nicene Creed, which proclaims one God in three consubstantial Persons, as well as the biblical testimony to the unity and divinity of God (cf. Matthew 28:19; John 14:9–11). The doctrine of the Trinity is not a theological abstraction but the revealed truth of who God is, affirmed universally by all orthodox Christian traditions.

Exaltation and Polytheism

LDS theology asserts that God the Father was once a mortal man who achieved divinity, and that human beings may also become gods through a process of exaltation. This is expressed in Doctrine and Covenants 132:20 and summarized by early Mormon teaching: “As man now is, God once was; as God now is, man may be.” Such a view introduces a multiplicity of divine beings and contradicts the biblical revelation of God’s eternal, uncreated nature. Scripture declares, “Before me no god was formed, nor shall there be any after me” (Isaiah 43:10, ESV), affirming the uniqueness and singularity of the Divine Being.

Denial of Scriptural Sufficiency

The LDS Church claims that the Bible has been corrupted and is incomplete. It elevates additional texts, The Book of Mormon, Doctrine and Covenants, and The Pearl of Great Price, to canonical status, asserting that these writings contain the fullness of the gospel. In doing so, the LDS tradition rejects the sufficiency of Sacred Scripture as held by the universal Church, which affirms the Bible as the inspired, complete, and trustworthy Word of God (cf. 2 Timothy 3:16).

A Reconstructed Christology

According to LDS teaching, Jesus Christ is the literal spirit brother of Lucifer, and He became divine through spiritual progression. This contradicts the confession of the Nicene Creed, which proclaims that Christ is “God from God, Light from Light, true God from true God, begotten, not made, consubstantial with the Father.” The Church has always affirmed that Christ is eternally divine and uncreated, fully God and fully man. In light of these doctrinal departures, the LDS Church must be recognized as a religious body that, while referencing Jesus Christ, does not share in the foundational truths that constitute Christianity. The use of Christian language is not sufficient to establish theological unity when the underlying doctrines contradict the revealed identity of God, the nature of Christ, and the message of salvation. Nevertheless, the Church approaches these differences with charity and clarity. Individual members of the LDS community often exhibit sincerity and devotion, which must be met with respect. However, theological clarity requires the faithful to distinguish between belief in the name of Christ and adherence to the truths Christ revealed.

As the Church teaches, true faith involves assent to divinely revealed truth, not merely a general spirituality or reverence for Jesus. The Catechism reminds us that “faith is a personal act, the free response of the human person to the initiative of God who reveals Himself” (CCC, 1997, paragraph 166). To defend Christian doctrine is not to condemn, but to witness faithfully to the truth. It is an act of love rooted in fidelity to Christ and a desire to bring all people into full communion with the Church He founded. As Pope Benedict XVI emphasized, “Truth and love are the two faces of the same gift, coming from God and flowing toward humanity. To renounce truth is to close the door to love” (Called to Communion, 2000, p. 125). This necessity of doctrinal boundaries is also a necessity of interpretation, because the faith can be distorted through interpretive freedom when interpretive limits are denied.

Limits of Interpretation

Whether one posits the existence of God or professes faith in Christ, the fundamental objective of this text is not to debate the existence of God but rather what is deemed to be faithful Christianity. Thus boundaries for what is considered to be faithful doctrine on a fundamental level must be defined. For if limits of interpretation is not defined, then intellectual honesty and logical consistency in fact and truth are meaningless. Interpretation is a necessary process in the life of any belief system, as it provides the framework through which meaning is drawn, transmitted, and applied across time. Yet, as hermeneutical philosophy makes clear, interpretation has limits that must be respected if a belief system is to remain faithful to its original truth claims. Hans-Georg Gadamer notes that understanding always involves a fusion of horizons, shaped by history, tradition, and language. However, this fusion is not infinite in scope.

There comes a point when interpretive freedom crosses into distortion, such that the resulting claims are no longer consistent with the originating belief (Stanford Encyclopedia of Philosophy, 2025). To illustrate this principle, one can consider the claims of the Church of Jesus Christ of Latter-day Saints, often referred to as Mormonism. While Mormonism makes use of Christian language and references the person of Jesus Christ, its interpretive framework diverges in fundamental ways from historic Christianity. For instance, the doctrine of God in Mormon theology is not consistent with the Christian confession of the Trinity as expressed in Scripture and affirmed by the creeds. The belief in a plurality of gods, the exaltation of humans into godhood, and the addition of extrabiblical scriptures such as the Book of Mormon constitute not merely interpretive developments but a departure from Christianity itself. To call such a system Christian is to stretch interpretation past the breaking point.

Just as one cannot claim allegiance to the laws of gravity while simultaneously denying their most basic principles, one cannot claim continuity with Christianity while abandoning its essential doctrines. This is where the deconstruction of claims becomes necessary. Simply stating, claiming, or teaching certain elements that resemble Christianity does not make a belief system Christian in nature. For example, Mormonism calls itself the Church of Jesus Christ of Latter-day Saints, but the presence of Jesus’ name in its title does not guarantee fidelity to Christian truth. Similarly, teaching sacraments does not make a religion authentically Christian if the underlying theology departs from the central truths of the faith.

Just as one could teach the laws of gravity incorrectly or distort them beyond recognition, thereby departing from the science of physics, so too can a religious group claim Christian categories while undermining the very truths that make them Christian. In both cases, the outward language or teaching cannot substitute for faithful adherence to the reality being described. Hermeneutics, therefore, must account not only for the educative nature of interpretation but also for its boundaries. As the Stanford Encyclopedia of Philosophy notes, interpretation is an ongoing, circular process involving whole and part, but it is also measured by validity and fidelity to what is being interpreted (Stanford Encyclopedia of Philosophy, 2025). When interpretations drift so far that they cease to preserve the essence of the original, they create something new altogether.

Thus, it is not an act of intolerance but of intellectual honesty to say that certain belief systems, despite superficial similarities, cannot rightly be considered Christian. The importance of recognizing the limits of interpretation is central to preserving the coherence and integrity of Christianity. Without boundaries, any belief that references Christ could be absorbed under the Christian identity, leading to confusion and dilution of the faith’s essential truths. Faithful Christianity requires that interpretations, while dynamic and contextual, remain tethered to the central tenets that define the religion: the Trinity, the Incarnation, the sacramental life, and the authority of Scripture and Tradition. Outside of these, the label "Christian" ceases to be meaningful. In this way, the limits of interpretation function not as restrictions to human freedom but as safeguards of truth. They protect the identity of Christianity from being dissolved into a mere category of religious pluralism. Just as hermeneutics teaches us to be vigilant about the prejudices and distortions that can shape understanding, so too must theology guard against interpretive leaps that undermine the very essence of the Christian faith. By doing so, Christianity maintains both its continuity with the past and its integrity for the future.

Conclusion

The examination of Christianity’s essential doctrines demonstrates that what unites the Catholic, Orthodox, Lutheran, Reformed, and other Protestant traditions is not uniformity of practice or ecclesial governance, but adherence to the foundational truths that have historically defined the Christian faith. Each of these traditions, despite disagreements, affirms the Trinity, the Incarnation, the atoning death and Resurrection of Christ, and the authority of Scripture. These are not secondary or negotiable features, but the criteria by which a faith is recognizably Christian. The Catholic Church itself acknowledges that while only the apostolic churches retain the fullness of truth, other communities that preserve these fundamentals share in the Christian faith in a real and meaningful way. By contrast, groups such as the Church of Jesus Christ of Latter-day Saints depart from these fundamentals to such a degree that it is not intellectually honest to classify them as Christian. While they may invoke Christ’s name and adopt Christian terminology, their doctrinal system, denying the Trinity, redefining Christology, and introducing polytheistic exaltation, moves beyond interpretation into invention. To label such beliefs as Christian is to strip the word of all coherence.

Intellectual honesty requires drawing boundaries, not to disparage others, but to preserve the integrity of language and meaning. Recognizing these limits is not an act of exclusion but of clarity. If every system that makes use of Christian symbols were accepted as Christian, the term itself would become meaningless. The consistency of Christianity across centuries, in spite of schisms and denominational differences, lies precisely in its fidelity to core truths. Where those truths are preserved, Christianity in some form endures. Where they are abandoned, no matter the vocabulary used, something different has been created. In this light, faithful Christianity is not about narrow sectarian claims but about intellectual and historical integrity. It is about affirming that words mean what they have always meant, that doctrines cannot be endlessly reshaped without consequence, and that truth requires boundaries. To uphold these essentials is not only a matter of faith but of reasoned honesty, ensuring that Christianity remains identifiable, coherent, and continuous with the revelation it professes to preserve.

References

Catechism of the Catholic Church. (1997). Catechism of the Catholic Church (2nd ed.). Libreria Editrice Vaticana. https://www.vatican.va/archive/ENG0015/_INDEX.HTM

Crossway Bibles. (2001). The Holy Bible: English Standard Version. Crossway.

Ratzinger, J. (2000). Called to communion: Understanding the Church today. Ignatius Press.

Shelley, B. L. (2013). Church history in plain language (4th ed.). Thomas Nelson.

The Church of Jesus Christ of Latter-day Saints. (2013). Doctrine and Covenants. The Church of Jesus Christ of Latter-day Saints. https://www.churchofjesuschrist.org/study/scriptures/dc- testament/dc

Zalta, E. N. (Ed.). (2025). Hermeneutics. In The Stanford Encyclopedia of Philosophy (Spring 2025 Edition). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/entries/hermeneutics/