Question: "Are there different religions within the Christian faith?"
Answer: With all the various denominations, schisms, associations, divisions, and sects within the Christian faith, some conclude that there are actually different Christian religions. That is not an accurate assessment. There is only one Christian religion. The different branches of the Christian faith are not separate religions, but rather distinct interpretations of what the Christian religion is supposed to be.
For example, Eastern Orthodoxy, Roman Catholicism, and Protestantism are very different in their beliefs and practices. At the same time, they all claim to follow the teachings of Jesus Christ; therefore, all three of them are commonly considered part of Christendom. Further, despite all of the differences, they actually agree on many important issues, such as the Trinity and the deity of Christ. While the differences in teaching and practice are important, they do not mean one is Christian and the others are not. Orthodoxy, Catholicism, and Protestantism cannot all be correct interpretations of Christianity, but all three can be considered branches of the Christian religion.
Within Protestantism, there are hundreds of different denominations and associations of churches. These are not different Christian religions, either, but different segments of the Protestant branch of Christianity. While there are important differences among the Protestant denominations, the similarities outweigh the differences. Protestant churches agree on the core doctrines of the Christian faith and the five solas, with their disagreements being over non-essential matters.
The most difficult aspect of this question is whether the “Christian” cults, such as the Mormons and the Jehovah’s Witnesses, should be considered different religions. These groups and many others are defined as cults since they deny one or more of the core doctrines of the Christian religion. At the same time, these groups claim to be Christian and do follow some of the teachings of Jesus Christ. Are their teachings on the person of Christ and the means of salvation biblically accurate? Definitely not. Does this put them outside of the Christian religion? That depends on how religion is defined.
If a religion is defined as the worship of a God or gods, then the question becomes whether a sect that denies the Trinity is worshiping the same God as Christians do. Are they worshiping an entirely different, non-triune god, or do they simply have a different interpretation of the nature of the God of Christianity? If a sect agrees with Christians that the mediator between God and humanity is Jesus Christ but has a different understanding of the nature of that mediator and how the mediation is accomplished, do they truly believe in the same mediator? If the answer is no, then we must begin to question whether Eastern Orthodoxy and Roman Catholicism should be considered Christian, considering they have a different view than Protestantism of how Christ’s mediation is accomplished.
Perhaps all of this is getting needlessly complicated. Ultimately, the answer to the question, “Are there different religions within the Christian faith?” depends on how you define the word religion. Whether Orthodoxy, Catholicism, Protestantism, and all the other Christian sects and cults should all be considered part of the Christian religion is not really the issue. The true issue is whether a particular division of Christianity is following the core truths of historic biblical Christianity, i.e., the Trinity, the true deity and true humanity of Jesus Christ, and salvation by grace alone, through faith alone, in Christ alone. Ultimately, true Christianity is more than a religion; it is a relationship with God the Father, made possible through Jesus Christ, and sealed by the Holy Spirit.