From the earliest centuries of its existence Christianity has lived with heresies, whose main characteristic is the denial of a truth of faith duly taught by the Catholic Church. The way bishops used, especially in the early centuries, to determine whether or not they were facing heresy, was to confront the doctrine taught with the rule of faith. This consisted in a measure that was based on the Sacred Scripture and the teachings of the apostles. Doctrine outside this measure was considered heretical. In order to prevent the proliferation of such doctrines and to punish those who caused disorder in the community, a code of laws was gradually developed in the Church. Hippolytus of Rome in the third century used the rule of faith in the fight against heretics. He is a controversial character, either because of the authorship of his works or for his strong personality, historically considered the first antipope because of the schism with Pope Callisto. This work demonstrates how Hippolytus fought the heresies that threatened Christianity in the first three centuries and how his works were important in defending the orthodoxy of faith, especially from the Philosophumena. It is also intended to present Hippolytus of Rome much more as a guardian of the faith than a schismatic, for at the end of his life he dies in exile reconciled to the Church, fighting the good fight and literally guarding the faith.