Pontifex Maximus (the High Priest or Chief Pontif) was thus called, not only because he was president of the whole college of priests or pontiffs, but also because he was the judge and superintendent of whatever related to the religion and sacred ceremonies of the Romans, whether in public or private. Accordingly it was the accustomed practice of the Senate to delegate its authority over all matters connected with the established worship of their gods to the Pontifex Maximus, and it was his duty to lay before the sacerdotal college, of which he was the head, all such questions as arose on the subject of their peculiar superstition, and to report their aggregate opinion thereon to the Senate. 

The Sovereign Pontificate was a dignity of Numa's creation, and the privilege of conferring it on any one was vested at first in the elective choice of the the Patricians; but in the process of time this, as well as other offices, which had once belonged exclusively to the nobles, was occasionally conferred on plebeian candidates by the suffrage of the people. Cicero, as if to indicate the immense influence of this office over the whole commonwealth, remarks that temples, altars, penates, gods, houses, wealth, and fortune of the people were subject to its power.

The Pontifex Maximus, under the Republic was, indeed, one of the principal personages of the state, and his functions were held in profound veneration. Entrusted as has been already observed with the direction of religious matters, of which he prescribed the ceremonies and explained the mysteries, it was the high priest who had the government of the Vestals, and in the inspection of every order of the priesthood. He dictated the form in which the public statues were to be couched; and professed the right of presiding at adoptions, was keeper of the public annals, regulated the calendar , and took to cognizance of certain cases relating to marriages. To him is solely appertained to grant dispensations; nor was he, except in very extraordinary cases, required to answer for his conduct either to the Senate or the people. Moreover, it was a dignity always held for life; he on whom it was once conferred continuing in it without even the form of renewal, and without acknowledging an equal in his office. This fact is evidenced by the circumstance of Lepidus having been allowed to hold it alone to the day of his death, although the people were desirous that Augustus should accept the office in his stead or at least share its exercise with the retired triumvir. Manifold, however, as were the prerogatives and decided as was the superiority of the power enjoyed by the Chief Pontif there were still bounds to his authority. the consent of the sacerdotal college was indispensable on several points to give validity to his proceeding; and appeals might be made, on questions of peculiar importance, as well from his decisions as from those of the college, to the people at large. 

Crassus, according to Livy, was the first Pontifex Maximus who contravened the ancient law which prohibited that high dignitary of religion from proceeding beyond the boundaries of Italy. Others afterwards availed themselves of the same relaxation, and a law (that of Vatinia) was passed which permitted the Grand Pontiff to draw lots for the provinces he was to govern. The consecration of this highly privileged and exalted officer was attended with ceremonies of a very extraordinary description.

There is a great distinction to be observed between the Pontifex Maximus of the Republic and the same high functionary under the imperial for m of government.

Julius Caesar united this office with the perpetual dictatorship of his own person. And from that period when (prudently declining the latter distinction) the emperor was invested with the honors of Sovereign Pontificate, and had increase the measure of its authority, the first emperors, know in the importance of such and office, for the hold on which it had on the feelings of the people, did not fail to attach it to their own persons, conjunctively with their other attributes and in conformity with a regulation made by Tiberius to whom the senate had yielded the privilege, the example of using the title of PONT. MAX was followed through an extended portion of the imperial series.

Until the reign of Balbinus and Pupiennus, who were chosen as joint Emperors at one and the same time, the Pontifactus Maximus was held by the principal sovereign alone, and not by his colleague or colleagues, in those instances wherein he had deemed it fit to associate one or more with him in the government. But the other might be simply Pontifices, and they often assumed the title. 

After the time of Balbinus and Pupienus it would seem that the dignity of Pontifex Maximus was divided amongst all the colleagues of the senior emperor, and that regardless of the (gradually fading) prerogatives of the senate, they all assumed to call themselves Grand Pontiffs, and to strike the designation on their respective coinage almost as a matter of course. 

The sacerdotal dignities of Paganism were retained for some time even by Christian emperors, as their coins serve to show. Doubtless this was don from motives of policy and expediency (the governing rule of most princes) on account of the state influence and the wealthy endowments still attached to the Pontificate of Rome. But Though, after the complete establishment of Christianity, the title of Pontifex Maximus ought naturally and consistently to have been abandoned by the emperors long before it was, it does appear to have finally and entirely ceased in the reign of Gratian.