A common argument among some Protestants is that the word catholic simply means “universal” and that anyone who believes in Christ is therefore part of the universal Church. This is not true. Only Catholics are Catholic, Orthodox Christians are not Catholic, and Protestants are not Catholic. Simply claiming belief in Christ is not enough. Correct doctrine matters. The earliest Christians held specific beliefs about Christ and the Church, and those beliefs help us understand what it historically meant to belong to the Church.
Romans 10:9 is sometimes cited to argue that anyone who believes in Christ and calls upon the name of the Lord will be saved and, therefore, belongs to the universal Church. By that argument, Mormons and Jehovah’s Witnesses would also have to be considered Christians. Both profess belief in Jesus, call upon His name, and regard Him as essential to salvation. So, according to this logic and definition of Catholic, Mormons, Jehovah’s Witnesses, the Church of God, and other groups would all be considered Christians simply because they believe in Jesus and call upon the name of the Lord. But if this principle is applied without regard to doctrine, it creates an obvious problem.
The response to this argument demonstrates why correct doctrine matters. Mormons and Jehovah’s Witnesses profess belief in Jesus, but they reject the historic Christian teaching that Jesus Christ is God. Therefore, the objection is that they believe in a fundamentally different understanding of Jesus and cannot simply be included within historic Christianity because they profess faith in Him.
This reinforces the Catholic point: professing belief in Jesus alone is not enough; what we believe about Jesus and His teachings matters. If correct doctrine did not matter, there would be no basis for excluding groups such as Mormons or Jehovah’s Witnesses simply because their understanding of Christ differs from historic Christian teaching. Once we acknowledge that someone can profess belief in Jesus while holding doctrines that place him outside historic Christianity, we have already acknowledged that doctrine matters. The question, then, is no longer simply whether someone believes in Jesus, but which doctrines are necessary to belong to the Church Christ established?
Christianity does not allow us to simply believe whatever we want. We cannot profess faith in Jesus, call upon the name of the Lord, and then disregard Christian doctrine. True Christianity involves believing what Christ and His Church taught. So, what is that doctrine? One way to answer that question is to examine the writings of the earliest Christians. When we look at Christianity during the first five centuries, we find Christians holding beliefs that are recognizably Catholic rather than distinctively Protestant. Their writings reveal specific doctrines about the Church, the sacraments, authority, and the Christian faith that many Protestants today do not accept.
Scripture presents one doctrine. The important question becomes: Which Church today teaches the faith handed down by the earliest Christians? Protestantism includes thousands of denominations and a wide range of theological beliefs, including significant disagreements over core doctrines such as salvation. These differences present a serious challenge to the claim that Protestantism collectively represents the one universal Church. If the Church is truly universal, there must be a common faith and doctrine that unites its members. Yet Protestant denominations disagree on baptism, salvation, the Eucharist, Church authority, and many other essential teachings. They cannot all represent one unified doctrine when their teachings contradict one another. Therefore, Protestantism as a collection of contradictory denominations cannot itself constitute the one universal Church united in one faith and doctrine.
The meaning of Catholic is not a mystery. The earliest Christians understood what it meant to be Catholic, and it never meant simply believing in Jesus or identifying as a follower of Christ. Belonging to the Catholic Church also involved holding to the doctrines handed down through the Church. The early Christians held specific beliefs, including infant baptism, baptismal regeneration, the Real Presence of Christ in the Eucharist, the sacraments, the authority and hierarchy of the Church, the Mass, and many other teachings that remain part of Catholicism today. These are doctrines the early Christians believed and that many Protestants reject.
You cannot claim to be Catholic while rejecting the teachings that historically defined the Catholic faith. Simply adopting the word catholic because it means “universal” does not make someone Catholic. It is true that the word catholic means “universal,” but the meaning of a word also depends upon the context in which it is used. Consider the word bank. Someone who says, “I’m going to the bank,” could mean a financial institution. A person going fishing might be referring to the bank of a river, while a basketball player might talk about banking a shot off the backboard. The same word can have different meanings depending upon its context. Likewise, simply pointing out that catholic means “universal” does not establish what it means historically and theologically to be Catholic.
The question is not simply whether the word catholic means “universal.” It does. The real question is what the earliest Christians meant when they identified the Church as Catholic. Being Catholic was never simply a matter of professing belief in Jesus while holding whatever doctrines one chose. It meant belonging to the Church and accepting the faith handed down from the apostles. If correct doctrine matters enough to distinguish historic Christianity from groups such as Mormons and Jehovah’s Witnesses, then doctrine also matters when determining what it means to be Catholic. To be Catholic, then, means more than just the word universal, it means embracing the faith the Catholic Church has taught from the beginning.
