If there are any Church historians out there, please correct me if I’m wrong. To the best of my knowledge the altar on two pillars was a very Roman concept that the Christians of Rome borrowed from the Roman temples. I know that once Christianity was legalized, many Roman temples were converted into churches. It would not suprise me if they kept the altar.
The Tau shaped altar dates back to ancient Israel. I was commonly used in many synagogues. Legend has it that it was resurrected by Pope Innocent III, though historical evidence points to St. Francis of Assisi.
Francis was present at the Lateran Council where heard Innocent make reference to the Tau in the writings of the Prophet Ezequiel. He brought the Tau back into use in our houses. It became the official cross of our early houses. The altars were built to form a Tau. The habits were cut in the shape of a Tau and crucifixes were often replaced by a Tau. The Tau is still in use by the Franciscans today. If you visit the Blessed Sacrament Shrine that Mother Angelica built, it has a Tau over the the roof, not a cross.
As I said, some people credit Innocent III with the Tau altar. But I have never seen anything built by him with such an altar. St. Francis and the early friars did build such altars. They were very interesting, because they were a few feet away from the wall, allowing the friars to gather around it, though the tabernacle sat on the altar for lack of space. There were no side altars or separate chapels in Franciscan houses. That was a Benedictine custom. The Benedictines did have the altars with the pillars, which would make sense, since their order dates back to to the first millenium. We’re younger.
The altars with the spires and nitches that are more familiar to us are very young. They came at the latter end of the Middle Ages. Often they resembled the outside of the great cathedrals built during the second millenium of Christianity.
Fraternally,
Br. JR, OSF