Titulus. In pagan times titulus signified an inscription on stone, and later the stone which marked the confines of property. Under Trajan it signified at Rome the limits of the jurisdiction of the priests, which is the germ of the meaning it bears in its ecclesiastico-archeological usage. Baronius explains that a cross sculptured on a church was the titulus which designated it as belonging to Christ, just as imperial property was indicated by the titulus fiscalis. Nothing remains to establish with certainty where the public Christian edifices of Rome before Constantine were situated. The earliest Christians assembled in the halls of private houses, and these oratories were therefore called ecclesiae domesticae. St. Paul mentions those at Rome and Corinth; in accordance with the most ancient Roman traditions, they were those of Aquilla and Prisca on the Aventine and the Ecclesia Pudentianae on the Viminal. These ecclesiae domesticae became the domus ecclesiae, and later domus Dei, i.e. the dominicum; and in this last period they received the name tituli, from the name of the founder or proprietor who held the property in custody for the Church. A populous Christian community, like that of Rome, by the end of the third century must have possessed a domus Dei, a social center which served as church, bishop’s residence, refectory, dispensary of charity, hospice, tribunal, and seat of the episcopal government, as was the case at Antioch, Carthage, Cirta, and elsewhere. In the fourth century all this was located at the Lateran, in the palace formerly belonging to Fausta, daughter of Maximinianus. The history of the Lateran begins with A.D. 313 and the most recent excavations there have revealed six Roman public and private edifices, but no Christian building earlier than Constantine. According to de Rossi the center of episcopal administration before the Lateran was a Christian building at San Lorenzo in Damaso, where in the fourth century the archives of the church were kept, and where now the central chancery (Cancellaria Apostolica) of the Papal government is situated.
According to the Liber Pontificalis, Pope Fabian about 250 divided the regions of Rome among the deacons, creating ecclesiastical districts. Probably these districts were provided with an edifice which was the center of administration and served that purpose for several centuries after Constantine, although no traces of such buildings survive. The diaconiae of the seventh century had nothing to do with these diaconal districts. In the fourth century, although the domus Lateranensis was the chief Christian edifice of the city, Rome possessed several places of assembly for the Christian community, which Ammianus Marcellinus calls conventicula christianorum. In time the unity of the presbyterium was broken and other ecclesiastical groups were created within the city, similar to the present city parishes independent of one another and dependent on a common center, under the direction of presbyters permanently appointed. To each one a basilica was assigned, dominicum domus Dei; the presbyters resided near this edifice, which in the language of archaeology is called titulus. The most ancient text which alludes to a titulus is the apology of St. Athanasius against the Arians (xx). The most ancient inscription relating to a titulus goes back to A.D. 377. The Liber Pontificalis attributes the foundation of the tituli to different popes of the first half of the fourth century, and this information, which seems genuine, is in part confirmed by inscriptions and by the names given to the churches. The tituli presbyterales therefore go back to the peace of the Church; they were not founded all at one time, but followed the progress of the Christian propaganda among the people of Rome. At the close of the fifth century there were twenty-five tituli; the Liber Pontificalis confirms this number and attributes their foundation to Pope Evaristus at the beginning of the second century. The last titulus recorded in the Liber is that of Vestina under Innocent I. The report of the Council of Rome (March 1, 499), contains the list of the names of the presbyters and their tituli. From this and from the report of a council held by Gregory the Great in 595, we know there were twenty-five tituli, which number, with few fluctuations, remained the same until about 1120 when it is given as twenty-eight. Three or four of the Gregorian tituli do not appear in the list of the council of 499, while the list of Pope Symmachus gives five which are not found in the council of 595. This difference is explained by establishing the location and the surroundings of the disputed tituli and identifying the tituli of Pope Symmachus with those of Pope Gregory. The titular churches are all found at a distance from the classic center of the City, and correspond to an epoch in which paganism preponderated at Rome. From the studies made and from existing monuments it is safe to attribute the foundation of many tituli to the third century and of most of them to the fourth.
After the presbyteral tituli came the diaconiae; these are not found in Roman documents before the seventh century. The Liber Pontificalis mentions them for the first time in the life of Benedict II (684-85). From the beginning the diaconiae were charitable institutions, and in a measure replaced for the Romans the frumentatio of Byzantine times and the doles of bread of the best days of the empire. They were established in the center of the city, with the materials, or on the site of, public edifices in a period when there was no longer a motive for building Christian churches away from the Forum or the Palatine. Under Pope Adrian (772-95) their number was fixed at eighteen. From the beginning of the twelfth century cardinal deacons adopted the names of their diaconiae and the number of eighteen was maintained until the sixteenth century. By the twelfth century cardinal deacons as well as the presbyters had long been dispensed from personal service at the tituli, since which time titulus of itself acquired a meaning analogous to that of the present time.