37. The following fact is also important. Learned men are divided as to whether the ancient practice of the western church was to have one or more altars in basilicas. Schelestratus declares that there was only one altar (Actor. Ecclesiae Orientalis, pt. 1, chap. 2 de Missa Privata in Ecclesia Latina). On the other hand Cardinal Bona, on the authority of Walfrid, chap. 4, shows that there were many altars in the Roman basilica of St. Peter (Rerum Lyturgicar, bk. I, chap. 14, no. 3). But if one considers the Oriental and Greek churches and basilicas, it seems evident that there was only one altar in them, and even today this is generally the case. This can be seen from the drawings of these churches in Du Cange, Constantinopoli Christiana; Beveregius, ad Pandectas Canonum; and Goarius in Euchologium Graecorum. Since in the Greek Church of St. Athanasius in Rome there are many altars, Leo Allatius in his letter to Joannes Marinus de Templis Graecorum recentiorum, no. 2 states with certainty that this church has no Greek form except the Bema or enclosure which separates the main altar from the rest of the church.

At this altar, only one Mass may be celebrated each day. This practice of the Greeks is mentioned by Dionysius Barsalibaeus, the Jacobite bishop of Amida, in Explanatione Missae, and by Cyriacus, Patriarch of the Jacobites, as the Jacobite Gregorius Barhebraeus says in his Directorio. Assemanus quotes these writers in his Biblioth. Oriental., vol. 2, p. 184, and vol. 3, part 1, p. 248. Cardinal Bona writes on this practice as follows: "They have a single altar in their churches, and they consider it wrong to repeat the Sacrifice in the sanctuary on the same day" (op. cit. chap. 14, no. 3).

Euthymius, Archbishop of Tyre and Sidon, and Cyril, Greek Patriarch of Antioch, several times during the pontificates of Clement XI, Benedict XIII, and Clement XII inquired whether they should allow this practice to continue which forbade the offering of a second Mass at the same altar on the same day. They always received the response that no changes were to be made and the ancient rite was to be preserved entire. The people came to believe mistakenly that the reason for not offering a second Mass at the same altar on the same day was that the second priest to celebrate Mass in the same vestments as the first was infringing a period of fasting. So in Our encyclical letter to the Greek Melchite Patriarch of Antioch and the Catholic bishops subject to him, We commanded them to inform the people that this was an error. They were to do this, however, without changing the practice of one priest only offering Mass on the same day at the same altar (constitution 87, Demandatam, Bullarii Nostri, vol. 1).