A few years ago, I watched a very fair-handed documentary on incorruptibles. It was not overtly skeptical/anti-Catholic as many of those documentaries are. It was based upon an officially sanctioned Vatican study, and most of the people they interviewed were the members of the study, believing Catholics.
Here’s the thing:
- Most people don’t go digging up dead bodies. Catholics do it to those considered for sainthood. While there have been some pretty remarkable incorruptibles (They say that St. Teresa Margaret Redi of the Sacred Heart still grows hair and fingernails) or particular preservations (St. Anthony’s tongue), most “incorruptibles” are your basic mummies. It’s very likely that many bodies around the world are “incorruptible,” but they don’t dig 'em up.
- Many of the “incorruptibles” were martyrs and ancient saints who died in caves or were buried in catacombs. The natural conditiosn of those areas, they explained, cold and sterile, led to natural preservation. When the bodies were exhumed for relics, people said, “Oh, look! They’re incorrupt!”
- Most of the other incorruptibles, the study found, had been embalmed. Now, here’s the tricky part: you get someone who’s poor, in an era when few, if any, were embalmed, being embalmed. Decades, or centuries later, when that person is beatified, they exhume the body and say, “oh! Look! An incorruptible!” Remember also that this is mostly a popular reaction.
Veneration of relics comes from the passage in Revelation about the martyrs being under the altar.
The Church supports veneration of relics, but she has never really given a statement on incorruptibles (just as St. Pio is the only person officially recognized by the Church as having had stigmata; the Church does not even officially recognize the stigmata of St. Francis of Assisi).
So, what really happened is that the people, and the church leaders, took the effort to have people embalmed if they expected them to be potential saints, just as religious orders today will preserve the “second class relics” of members they expect to have a potential of canonization.
They get embalmed, and preserve better than their contemporaries, and get dug up. When the body is dug up, the church officials realize it’s because of embalming, but the public immediately yells “Incorruptible!” (We saw this happen when they exhumed Bl. John XXIII).
All that said, there are some incorruptibles that the commission could not explain.
However, the final analysis was that the phenomena of “incorruptibles” is not so much supernatural intervention to identify saints as the intervention of the hierarchy and laity of the individual’s time to mark out someone they believed to be saintly.