There is one body and one Spirit, just as you were called
to the one hope of your calling, one Lord, one faith,
one baptism, one God and Father of all,
who is above all and through all and in all.
Ephesians 4, 4-5

In Protestantism, it is believed that anyone who professes faith in Christ automatically becomes a member of the Church that Christ established, independent of their specific denomination. This view underscores the idea that the Church is essentially a spiritual (pneumatic) body made up of all committed, baptized believers. Conversely, within Catholicism, the Church is recognized as a visible and hierarchical institution, founded by Christ, and does not accept the existence of independent, autonomous denominations with varying beliefs. In Catholic doctrine, mere valid baptism is not sufficient for membership in Christ’s body; separation from this body can occur through actions such as apostasy, heresy, schism, or excommunication from the Catholic Church. The Catholic Church is seen as one, holy, and apostolic since the event of Pentecost. Additionally, the Protestant perspective often emphasizes the notion that the Church is invisibly united in the Holy Spirit, despite appearing divided in the world on key issues related to faith and morals. This understanding contrasts with the Catholic view of a unified, visible Church.

Now you are Christ’s Body, and individually members of it. And God has appointed in the Church, first apostles, second prophets, third teachers, then miracles, then gifts of healings, helps, administrations, various kinds of tongues. All are not apostles, are they? All are not prophets, are they? All are not teachers, are they? All are not workers of miracles, are they? All do not have gifts of healings, do they? All do not speak with tongues, do they? All do not interpret, do they? But earnestly desire the greater gifts.
1 Corinthians 12, 27-31

St. Paul describes the Mystical Body of Christ as a unified entity that parallels the organization of a physical body, with various members each serving distinct functions. This concept emphasizes the importance of a cohesive body made up of diverse parts that work together to maintain overall harmony. According to Ephesians 1:22, God the Father placed everything under the authority of Christ, who serves as the head of the Church, referred to as His body, representing the fullness of Him who encompasses all. The body of Christ consists of many members, each with unique roles and responsibilities. While some spiritual gifts may be regarded as greater than others, it is crucial to recognize that all members are interdependent, contributing to the effective functioning of the body as a whole.

The single body operates as a hierarchical structure in which each subordinate role is essential for maintaining the unity and harmony of the entire system. At the top of this hierarchy is Christ, serving as the head of His body. This head, along with its various members, collectively forms a single body that shares a divine life. The concept is emphasized in Ephesians 4:15-16, which states, "Rather, speaking the truth in love, we are to grow up in every way into Him, who is the Head, Christ. From Him, the whole body, joined and knit together by every joint with which it is supplied, grows and builds itself up in love as each part operates effectively." This passage illustrates the significance of each member's contribution to the overall growth and functionality of the body as a cohesive unit.

The Holy Spirit is often described as the Church's soul, serving as its vital source of life and animation. While the Holy Spirit itself is invisible, the Church manifests in a tangible form composed of both spiritual and physical elements, represented by its members. As noted in 1 Corinthians 12:13, all believers are baptized into one body by the Holy Spirit, transcending divisions such as ethnicity or social status, and they share in the Spirit's presence. The Holy Spirit acts as the life principle of the mystical Body of Christ, fostering unity among believers in faith. Each member of the Church is connected to Christ through their incorporation by the Holy Spirit. Thus, any division or disagreement within the Church should not be attributed to the Holy Spirit, but rather to the behavior of certain members who may become overly assertive or self-satisfied. Such attitudes can lead to conflicts, much like a body affected by an external threat, analogous to a virus introduced by an outside force, which disrupts harmony and order within the Church.

In Galatians 2:20, Paul states, “It is no longer I who lives, but Christ lives in me.” This phrase highlights the concept of our union with Christ within the context of the Church, which is often referred to as his mystical Body. It is important to interpret this statement not in an individualistic manner, such as the “Jesus-and-me” approach, since this understanding can contribute to a certain indifference among some Protestants toward joining the Catholic Church. The fullness of our union with Christ is realized through our incorporation into his mystical Body, which is the singular Church established on Peter the Rock. This formation allows all members to share a common faith and baptism. Additionally, Jesus metaphorically describes the Church as a "city set on a hill" that cannot be hidden (Mt 5:14), emphasizing its visibility and importance in the world.

The concept of the Church as an invisible corporate entity united in the Holy Spirit contrasts with the reality of numerous self-governing Christian denominations that exist with fundamentally differing beliefs. This perspective does not align with the vision that Jesus intended for His followers, as highlighted in John 17:11, 21, and 23. According to scripture, Jesus entrusted Peter, and through him the apostles, with the authority to "bind and loose" (Mt 16:19; 18:18). This authority necessitates a hierarchical structure within the Church, leading to a visible unity among believers. The acts of binding and loosing are inherently visible and are meant to take place within a single community under Jesus' guidance, as indicated in John 10:16, where it is emphasized that there is one flock that follows His design.

The gifts he gave were that some would be apostles, some prophets,
some evangelists, some pastors and teachers, to equip the saints for
the work of ministry, for building up the body of Christ,
Ephesians 4, 11-12

The Church founded by Christ is characterized by a visible unity that stems from a shared faith, common celebration of sacraments, and a global ecclesial hierarchy. This structure has been inherited from the apostles, with authority divinely bestowed upon our Lord. In this context, Jesus serves as the invisible Head of the Church, while Peter and his ordained successors in Rome are recognized as the visible heads on Earth. The unity of each member within the visible hierarchy is contingent upon their alignment towards a singular visible leader. If the visible leadership comprises multiple heads from different denominations within an invisible Church, the visible hierarchies will lack essential unity and will only be accidentally connected.

The Protestant understanding of the Church posits that it cannot be viewed as a singular infallible corporate entity directed by the Holy Spirit in all matters of truth. Instead, the varying doctrines and practices within different denominations arise from individual interpretations and prevailing popular opinions. Consequently, there is no overarching unity in the Church's teachings beyond the fundamental principles outlined in the early Apostles' Creed. Furthermore, unlike the early Church and the apostolic era, there is no unified and dependable teaching authority present today.

The visible fragmentation within the pneumatic Church is characterized by the presence of multiple heads and distinct hierarchies representing various denominations, each adhering to different beliefs on matters of faith and morals. This situation creates noticeable disunity, as these diverse authoritative entities often hold opposing and unresolved theological views, which can hinder a cohesive expression of faith. A central question arises: which denominational hierarchy can legitimately assert that it is guided and protected by the Holy Spirit, especially in the absence of a single universal authority appointed by Christ and endowed with the charism of infallibility in extraordinary matters of faith and morals?

The issue of denominational diversity has been a significant concern for Protestants since the Reformation led by Martin Luther. This period marked the beginning of the establishment of numerous independent and autonomous denominations within Christianity. While this diversity may be seen as an expression of faith, it is often viewed as contributing to a lack of unity within the body of Christ, resulting in a perception of continual fragmentation. This situation raises important questions about the role of the Holy Spirit in such widespread confusion, which seems to contradict the Church's mission of progressively revealing the fullness of divine truths, as emphasized in John 16:12-13.

Protestants typically do not subscribe to the belief that Christ established a single visible and hierarchical Church under one visible head, specifically Peter, who is considered the rock of the Church. According to this view, unity among the apostles was essential for their teachings to be infallible or free from significant error, as supported by the guarantee of the Holy Spirit in Acts 15:1-35. However, it is interesting to note that each Protestant congregation is typically led by a head pastor, and mainstream denominations often have their own visible hierarchies. While the Church as a whole is considered invisible, each Protestant denomination and congregation has a defined leadership structure to maintain unity in matters of faith and morals among its members. Nevertheless, this has resulted in visible and tangible divisions within Christendom concerning these same matters.

This situation highlights a perceived inconsistency within Protestantism, particularly from the Catholic Church's perspective, which emphasizes the importance of maintaining Church unity since the time of the apostles. The Catholic Church asserts that Christ did not intend to establish a fragmented religious movement composed of numerous denominations. Instead, these denominations are viewed as human-made entities that mirror a democratic political system, where individual freedoms of speech and conviction are prioritized to a degree that may overshadow the notion of the Church as a unified kingdom and monarchy.

In the context of Christian ecclesiology, it can be argued that a composite body requires a unified visible hierarchy centered around a single, identifiable leader to function as a cohesive entity. In contrast, the Protestant perspective positions each denomination as both a visible and an invisible body within the broader "invisible" Church. Each Protestant denomination is seen as a reflection of the ideal Church that aligns with traditional Christian teachings. However, this perspective may raise questions about the consistency of their practice, as it diverges from the ancient Catholic tradition that many Protestant denominations reject, suggesting that the beliefs held may not be fully realized in their practices.

Our Lord and King, Jesus Christ, intended for His Church to function as a unified, composite whole—a hierarchical and visible body led by one visible head who acts as His representative on Earth. In His infinite wisdom, Christ understood that without a unified hierarchy, or if such a structure were abandoned at any point in history, it would become impossible to maintain the unity of faith and the coherence of sacraments among believers.

The Apostle Paul illustrates this concept by describing the Church as one visible body made up of individual members, each with its role, working together under a defined hierarchy of believers—an ordered structure designed to exemplify divine unity. In contrast, the Protestant paradigm presents a challenge to this model by promoting the idea of one invisible body of Christ that exists alongside separate visible bodies, each with its own distinct hierarchies and leaders, resulting in numerous visible heads. This fragmentation raises profound questions about how the one Spirit or soul could possibly animate such a diversely composed and incomposite body, leading to divisions that are fundamentally contrary to the principle of unity that Christ advocated.

As scripture reassures us, “God is not the author of confusion but of peace” (1 Cor 14:33). It is important to note that all the churches established by the apostles and their successors in the first century were part of the singular, visible, and universal (catholic) Church. This Church recognized Peter as its one visible head and vicar of Christ on earth, ensuring a clear line of authority and teaching that was intended to guide the faithful in all matters of doctrine and practice. This structure not only preserved the integrity of the faith but also fostered a deep sense of community and shared mission among the early Christians, establishing a foundation that continues to be significant for believers today.

For just as we have many members in one body and all the members do
not have the same function, so we, who are many, are one Body in Christ,
and individually members one of another.
Romans 12:4-5

Paul issued a stern warning to the faithful, urging them to steer clear of those who sowed discord within the Church by disregarding apostolic teachings (Rom 16:17). While his primary focus was on countering the influence of the Judaizers—who sought to impose Jewish law upon Gentile believers—false teachers posed a broader and equally perilous threat to the congregation to which John was writing. Specifically, John cautioned his community against extending hospitality to false teachers, particularly the Docetists, whose beliefs fundamentally distorted the nature of Christ. Though his admonitions may have seemed severe and contrary to the spirit of Christian love, the ramifications of their heretical teachings on Christology threatened to undermine the very foundation of faith within his flock (1 Jn 4).

The New Testament was meticulously composed to authenticate and preserve the core message of the apostles, serving as a corrective to prevailing misunderstandings and fostering doctrinal unity across the early Church. Upholding the Apostolic Tradition became imperative to safeguard the integrity of Christian doctrine, ensuring that the Church remained united and resilient against fragmentation into diverse sects or denominations. Such divisions might arise from individuals with no legitimate apostolic authority derived from Christ, leading believers away from the true teachings laid out by the original apostles. In this context, preserving doctrinal purity was vital for maintaining a cohesive and authentic expression of faith within the nascent Christian ecclesia.

The concept of one Spirit, faith, and baptism emphasizes the necessity of a singular, visible Church characterized by doctrinal unity. For example, all faithful Catholics universally accept beliefs such as Mary being the Mother of God and the practice of infant baptism. In contrast, these beliefs are not uniformly held within Protestantism or various denominations of Christianity. Jesus acknowledged the challenges the Church would face, stating that the gates of hell would attempt to overcome it but would ultimately not succeed, as he would establish his Church upon Peter, referred to as the rock, and grant him the keys to the kingdom (Mt 16:18). Historically, Satan attempted to undermine the Church by fostering doctrinal disunity. The early New Testament church faced significant challenges from dissenting sects such as the Docetists and Judaizers, who contested the Church’s apostolic teaching authority. These groups contributed to divisions and conflicts among members in different Christian communities.

In his letters, Paul passionately exhorted the church in Philippi to remain steadfast in one spirit and purpose, urging them to unite in their efforts to uphold and promote the authentic faith of the gospel (Phil 1:27). He emphasized the importance of their collective strength, calling them to work together as a cohesive body of believers. Similarly, in his correspondence with the Thessalonians, he implored them to stand firm and hold fast to the traditions and teachings they had received from the apostles, who were directly appointed by Christ (2 Thess 2:15). The apostle faced significant challenges, particularly in response to the rise of false teachings that threatened to infiltrate and sow discord within the Church across various regions. Recognizing the danger these distortions posed to true doctrine, Paul earnestly prayed that all Christians would be united in mind and spirit, striving together in harmony (Phil 2:2).

When Paul ordained Timothy as bishop, he imparted crucial warnings about individuals who sought to stir controversy and engage in disputes that undermined the foundational beliefs shared by the faithful. He strongly reminded Timothy of his responsibility to safeguard these teachings and to diligently pass down the rich inheritance of doctrine that had been entrusted to him by the universal apostolic authority of the Church (1 Tim 6; 2 Tim 2:2). This legacy was vital for maintaining the integrity of the Christian faith in an increasingly diverse and challenging landscape.

The Apostle Paul recognized the Church as the Bride of Christ, as mentioned in Ephesians 5:25. This concept supports the idea that there is only one unified visible Church, which implies that Christ has one bride, rather than multiple brides. Additionally, Christ is portrayed as the Head of one body—the Church—rather than numerous bodies or denominations, each with its own leaders and often differing doctrines. Peter also emphasized the importance of unity among believers, urging them to have unity of spirit (1 Pet 3:8). His exhortation indicates an acknowledgment of the Church as a singular, hierarchical body. Achieving unity of spirit and mind is seen as feasible only if there is a central teaching authority established by Christ, built upon the foundation laid by the apostles and their legitimate successors in the episcopate.

Respect for this apostolic teaching authority is essential to prevent discord and potential schism. Various scripture references, including 2 Corinthians 2:17, 1 Thessalonians 5:12-13, and Hebrews 13:7, emphasize the need for adherence to this teaching authority to maintain ecclesiastical harmony. Through the principle of apostolic succession, this divine office has been preserved and will continue to be guided by the Holy Spirit. This ensures the faithful transmission of tradition and doctrinal unity until the return of Christ in glory, as noted in Matthew 28:16-20.

In his prophetic vision of the Church, Daniel articulates that individuals from all nations and languages will serve the kingdom of God (Daniel 7:14). This singular entity is recognized as the Catholic Church. The term "catholic" derives from the Greek word "katholikos," which means universal, indicating that the Church is a comprehensive assembly comprising diverse peoples from various nations and cultures. Despite the global demographics of its members, which include a vast array of ethnic backgrounds and liturgical traditions, the Church unites them in a singular faith, in communion with the Vicar of Christ, sharing one mind and one spirit. This unity persists in the face of challenges such as internal dissension, discord, or scandal, all of which may arise due to the influence of darkness; however, these conflicts do not threaten the Church's fundamental existence.

The Catholic Church has endured for nearly two thousand years, outlasting numerous historical empires and maintaining its presence across continents. Its resilience is rooted in the belief that Christ, as its Head, governs the Church and guides its mission until His glorious return. The promise of Christ’s return heralds the perfect unity of Christendom, culminating with the second coming of Christ at the end of this Messianic age. This future fulfillment is anticipated to bring all believers together in an unparalleled communion of faith, reflecting the divine purpose established from the beginning of creation.

Early Sacred Tradition​

St. Ignatius of Antioch (c. A.D. 110)
Epistle to the Smyraens, 8

“See that ye all follow the bishop, even as Jesus Christ does the Father, and the presbytery as ye would the apostles; and reverence the deacons, as being the institution of God. Let no man do anything connected with the Church without the bishop. Let that be deemed a proper Eucharist, which is administered either by the bishop, or by one to whom he has entrusted it. Wherever the bishop shall appear, there let the multitude [of the people] also be; even as, wherever Jesus Christ is, there is the Catholic Church. It is not lawful without the bishop either to baptize or to celebrate a love-feast; but whatsoever he shall approve of, that is also pleasing to God, so that everything that is done may be secure and valid.”

St. Irenaeus (A.D. 189)
Against Heresies, 5:20

“Those, therefore, who desert the preaching of the Church, call in question the knowledge of the holy presbyters…It behooves us, therefore, to avoid their doctrines, and to take careful heed lest we suffer any injury from them; but to flee to the Church, and be brought up in her bosom, and be nourished with the Lord’s Scriptures. For the Church has been planted as a garden (paradisus) in this world; therefore says the Spirit of God, ‘Thou mayest freely eat from every tree of the garden,’ that is, Eat ye from every Scripture of the Lord; but ye shall not eat with an uplifted mind, nor touch any heretical discord.”

St. Cyprian of Carthage (A.D. 250)
To the Lasped, Epistle 26/33

“Our Lord, whose precepts and admonitions we ought to observe, describing the honour of a bishop and the order of His Church, speaks in the Gospel, and says to Peter: I say unto thee, That thou art Peter, and upon this rock will I build my Church…Thence, through the changes of times and successions, the ordering of bishops and the plan of the Church flow onwards; so that the Church is founded upon the bishops, and every act of the Church is controlled by these same rulers. Since this, then, is founded on the divine law, I marvel that some, with daring temerity, have chosen to write to me as if they wrote in the name of the Church; when the Church is established in the bishop and the clergy, and all who stand fast in the faith.”

St. Basil the Great (A.D. 375)
Commentary on Isaiah, 2:66

“‘And in the last days the mountain of the house of the Lord shall be prepared on the top of the mountains’ The house of the Lord, ‘prepared on the top of the mountains,’ is the church, according to
the declaration of the apostle, ‘Know,’ he says, ‘how thou oughtest to behave thyself in the house of God, which is the church of the living God’ Whose foundations are on the holy mountains, for it is built upon the foundation of the apostles and prophets. One also of these mountains was Peter, upon which the rock the Lord promised to build his church.”

He that is not with me is against me:
and he that gathers not with me scatters.
Luke 11, 23