Ordo (order), as applied to the clergy, has been the occasion of controversy. Many contend that it is adopt- ed from the Roman language, and used by Tertullian and others in the classic sense, to exhibit the patrician rank of the clergy, like the ordo senatorius of the Eo- inans. The fact is, that the word is used to denote the difference between the clergy and the people — the ordo ecclesiasticus and the laity ; and in this sense it lias been understood since the close of the second century. See Riddle, Christian Antiquities, p. 203, 212.
Ordo Romanus is the name given to every rule of the Romish Church in general, and particularly to the rules concerning worship. Like tu^iq, SiaTa^ig, the rule and its exposition, or tuktikoq (jaicTiKr], sc. /3i'- jSXoe)) or ordo or ordinarius (sc. liber), or ordinnle and ordinalis (sc. liber) (Du Fresne), signifies a collection of rules for worship. In the course of time there appear- ed many such libelli, which, in so far as they related to the same subject, were compiled together. The exact time when these different libelli appeared is not ascer- tained, nor that of their compilation. As early as the 5th century there was a distinction between the sacra- mentarium, containing the prayers for the Eucharist, the antiphonarius (liber), with the liturgic chants, and finally the ordo, constituting the ritual. See F. Probst, Verwaltung d. hochheiligen Eucharistie (Tubing. 1853), p. 9 sq.
Various ordines appeared in the different churches, but they were gradually all superseded by the Roman 07-do, for the popes as early as the 5th century used ev- ery exertion to have the worship conducted everywhere according to the usages of Rome. The subsequent publishers of rituals often confounded the Roman with other rituals, hence the number of those which were published. See ]\Iabillon, In Ordinem Romanum com- mentarius, preceding his edition of the Antiquilibri ritu- ales sanctee Romanw ecclesia, in the Museum Italicum, 1. 11 (Paris, 1724, 4to). The oldest Ordo Romanus is attributed to bishop Gelasius (f 496) by Mabillon (as above) and Muratori, Liturgia Romana vetus (Venice, 1748), i, 289 sq. Yet from the Epist. I of Innocent I, Ad Decentium, in 416 (in cap. 11, dist. xi), there appears to have existed an older ordo, which is now lost. The ordo attributed to Gelasius, although it often refers to Leo I, seems to have been written by an unknown au- thor in the time of Felix III, the predecessor of Gela- sius (Biihr, D. christlich-romische Theologie, p. 364). This ordo, as well as that published by Mabillon and Muratori as No. 1, was in general use in the 9th cen- tury, as is proved by the use made of it b}-^ Amala- rius. These two ordines, together with those pub- lished as Nos. 3 and 4 by Mabillon, and which are of somewhat later date, treat of the missa pontijicalis. The ordines 5 to 10 of Mabillon, which are of much later origin, and belong probably, in part at least, to the 11th century, refer to the missn episcopalis, tlie ordo scrutinii ad electos, qualiter debeat celebrari (in bap- tism), the forms of ordination for the different degrees, as also the ordo, qualiter agendum sit quinta feria in
cana Domini, feria sexta Parasceve, in sabbato sancto, ad 7-econciliandum pcenitentem, ad visitandum irifirmum, ad consignandum pueros sive infantes, ad ungendum in- firmos, ad communicandum infrmos, ordo sej)eliendi clericos Romance fraternitatis. We now possess but fragments of most of these ordines. It is therefore doubtful whether Bernard of Pavia, who quotes numer- ous passages of the Ordo Romanus in his Breviarium Extravagantium (which are also given in the collection of decretals of Raymundus a Pennaforte, c. ix, De officio archidiaconi, i, 23 ; c. ix, De officio primicerii, i, 25 ; c. ix, De officio custodis, i, 27), obtained or borrowed them from an ancient Ordo Romanus or from a later one. At any rate, those passages are not to be found in any of the printed oi-dines.
Among the oldest published Ordines Romani are those of George Cassander (Colon. 1559, 1561 ; also in his works, Paris, 1616), Melchio Hittorp (Colon. 1568), and G. Ferrarius (Rom. 1591 ; Paris, 1610, 1624, fol). About 1143 Benedict, a canon and chorister of St. Peter's, com- piled an oi-do entitled Liber jwllicitus ad Guidonem de Castello (the future pope Celestine II, then cardinal of St. Marc). He describes the divine worship for the whole ecclesiastical }"ear, with special reference to the papal affairs (published in Mabillon, No. 11). At the Council of Pavia, in 1160, the clergy made use of a liber de vita et ordinatione Romanoi-um pontificum (Pertz, Monumenta Germ, iv, 126). The Ordo Romanus con- tained also the forms to be used at the coronation of the emperor. On the form used in 1192 see Pertz (p, 187 sq.), Mabillon, and Martene. This form was adopt- ed in the ordo %vritten in 1192 by cardinal Cencius (Mabillon, No. 12). Since the 13th century the ex- pression Ceremoniale Romanum seems to have gradu- ally taken the place of that of Ordo Romanus. Greg- ory X (1272) caused a new one on the election and the functions of popes to be compiled (Mabillon, No. 13). A subsequent one appeared in the middle of the 14th century (Mabillon, No. 14), which Mabillon attributes to cardinal Gaietanus. One on the ecclesiastical func- tions of the Roman clergy was compiled by Petrus Amelius, bishop of Sinigaglia (f 1398) ; a larger work of the same kind, by Augustinus Piccolomini, was pub- lished at Venice in 1516, with the sanction of Leo X, under the title of Rituum ecclesiasticorum sive sacrarum ceremoniarum libri tres. The Pontifcale Romanum of Clement VIII (1596), and his Ceremoniale Episcoporum (1600, often reprinted and revised), have finally taken the place of the old Ordines Romani. At present there is an ecclesiastical calendar published each year in ev- ery diocese, which fills the place of an Oi-do Romanus, and generally bears the title Ordo officii divini juxta ritum Romanum, or Juxta nibricas breviai'ii et missalis Romani atque decreta sacrm rituum congregationis.