As a church history professor, I am sometimes asked how certain practices developed. For example: When did the Roman Catholic (and Eastern Orthodox) emphasis on praying to saints and venerating relics and icons begin?

A somewhat obscure, but extremely helpful book by John Calvin answers that question directly.

In his work, A Treatise on Relics, Calvin utilizes his extensive knowledge of church history to demonstrate that prayers to the saints, prayers for the dead, the veneration of relics, the lighting of candles (in homage to the saints), and the veneration of icons are all rooted in Roman paganism. Such practices infiltrated the Christian church after Christianity became the official religion of the Roman Empire in the fourth century.

Here is an excerpt from Calvin’s work that summarizes his thesis:

Hero-worship is innate to human nature, and it is founded on some of our noblest feelings, — gratitude, love, and admiration, — but which, like all other feelings, when uncontrolled by principle and reason, may easily degenerate into the wildest exaggerations, and lead to most dangerous consequences. It was by such an exaggeration of these noble feelings that [Roman] Paganism filled the Olympus with gods and demigods, — elevating to this rank men who have often deserved the gratitude of their fellow-creatures, by some signal services rendered to the community, or their admiration, by having performed some deeds which required a more than usual degree of mental and physical powers.

The same cause obtained for the Christian martyrs the gratitude and admiration of their fellow-Christians, and finally converted them into a kind of demigods. This was more particularly the case when the church began to be corrupted by her compromise with Paganism [during the fourth and fifth-centuries], which having been baptized without being converted, rapidly introduced into the Christian church, not only many of its rites and ceremonies, but even its polytheism, with this difference, that the divinities of Greece and Rome were replaced by Christian saints, many of whom received the offices of their Pagan predecessors.

The church in the beginning tolerated these abuses, as a temporary evil, but was afterwards unable to remove them; and they became so strong, particularly during the prevailing ignorance of the middle ages, that the church ended up legalizing, through her decrees, that at which she did nothing but wink at first.

In a footnote, Calvin gives specific examples of how Christians saints simply became substitutes for pagan deities.

Thus St. Anthony of Padua restores, like Mercury, stolen property; St. Hubert, like Diana, is the patron of sportsmen; St. Cosmas, like Esculapius, that of physicians, etc. In fact, almost every profession and trade, as well as every place, have their especial patron saint, who, like the tutelary divinity of the Pagans, receives particular hours from his or her protégés.

You can read the entire work on Google Books.

Calvin’s treatment includes a historical overview, quotes from the church fathers, and even citations from sixteenth-century Roman Catholic scholars. The result provides a compelling case for the true origin of many Catholic practices.

Calvin’s conclusion is that these practices are nothing more than idolatrous superstitions, rooted in ancient Roman paganism. Even today, five centuries later, his work still serves as a necessary warning to those who persist in such idolatry. Hence his concluding sentence: “Now, those who fall into this error must do so willingly, as no one can from henceforth plead ignorance on the subject as their excuse.”