You may hear people claim that the Catholic Church was started by the emperor Constantine in 313. Constantine’s Edict of Milan simply made legal the Christianity that already existed. Here are some facts about those early Christians you probably are not being told by non-Catholic sources:
The early Christians venerated saints and relics, which is a biblical principle. For example, contact with the bones of Elijah brought a dead person back to life. In Acts we read how people were healed by touching Peter’s handkerchief and even his shadow. Pagans took issue with early Christians keeping the bones of dead people close at hand. The usual practice was to keep dead people at a distance. Christians in all parts of the world have venerated saints and relics throughout history. Constantine did not invent these practices. They were already in practice from antiquity.
Interestingly, although churches were built above the relics of important saints, no one built a church above the bones of Mary, the mother of Jesus. She has no grave to visit. There was no corpse to be found. Surely, her dead body would have been venerated by these early Christians if it was still on Earth.
The early Christians were accused of cannibalism due to their liturgical practices. The Catholic Church is the only church still accused of cannibalism, primarily by non-Catholic Christians seeking to disprove the authenticity of Catholicism.
The early Christians relied primarily on the oral tradition and the successive authority of the apostles, not on scripture alone as their final authority. Not until the late 300s was the canon of scripture compiled and authorized by the bishops of the Catholic Church. Neither Constantine nor the Christians had ever heard of Sola Scriptura. Oral Tradition continued to be the primary means of Christian teaching until the Protestant Reformers asserted the novel idea of Sola Scriptura and used the invention of the printing press to promote it. Ironically, Sola Scriptura became a foundational, Protestant tradition which cannot be affirmed by scripture alone.
The early Christians already referred to themselves as “catholic” well before Constantine came along and legalized Christianity. The early Christians saw themselves as one body, not as separate ecclesial communities with conflicting doctrines. This can be observed in the works of the early church fathers.
Ignatius, the first century bishop of Antioch, is known for his use of the Greek word katholikos (καθολικός), meaning “universal”, “complete” and “whole” to describe the church, writing:
Wherever the bishop appears, there let the people be; as wherever Jesus Christ is, there is the Catholic Church. It is not lawful to baptize or give communion without the consent of the bishop. On the other hand, whatever has his approval is pleasing to God. Thus, whatever is done will be safe and valid.— Letter to the Smyrnaeans 8
Early Christianity was distinctly Catholic before and after Constantine came along. Constantine’s Edict of Milan didn’t start Catholicism; it simply let it out of its cage. As Saint Cardinal Newman, a convert to Catholicism once said, “To be deep in history is to cease to be Protestant.”