He [Numa, Rome's second King] foresaw that in a martial community like Rome future Kings were likely to resemble Romulus rather than himself and to be often, in consequence, away from home on active service, and for that reason he appointed a priest of Jupiter on a permanent basis, marking the importance of the office by the grant of special robes and the use of the royal cural chair. This step ensured that the religious duties attached to the royal office should never be allowed to lapse (Livy I.20)
This passage from Livy's first volume- slightly before the discussion of Ancus Martius that occupied my last post- refines it. Livy describes one of the key reforms of Numa- the institution of a priesthood of Jupiter- and in doing so what he brings up is the notion of what in his eyes early Roman Kingship actually was. Part of the role of the King for Livy is the 'religious duties' that attach to the person of the King. A priest might maintain their authority through the use of a royal chair- a King needed a deputy in religious matters for when he was away from the throne. It is an interesting reflection- because what it reminds us of is a feature of the Roman state right up until the time of Livy and beyond. Religious and political power have been split in Europe since the days of the early medieval papacy- but in the Roman state they were not. The priest was another magistrate- this goes back through the Republic where the Pontifex maximus (chief priest) was a political officer as well and aristocrats held priestly roles and kept rituals going- Livy later discusses one such ritual that reminded Romans of the patriotism of the Horatii (I.26) and such rituals emphasized the continuity of the Roman state and the important role that various families had played in it. (We shall think about the Horatian tradition later because it is interesting in its own right.)
Was Livy right- could the origins of this priestly power lie with Numa? One suspects that religion and politics have been married for a long time- but we cannot prove it. Rather I would see this account as less an account of the way that things actually happened- than an account of the way things might have happened. To say such and such began with Numa allows Livy to do two things- he can bring forwards a reason for it happening like that- the absense of the King from Rome justifies the creation of a Royal Priestly office which would continue through the consulate. It also allows him to project that office back into a past so ancient as to be beyond political- it establishes the priesthood as a norm in Roman politics- tied to no one regime (it is not Republican but Royal) and thus to be continued under the Principate- and as something that cannot be questioned. Like 17th Century English lawyers who projected laws about feudal tenure back into the time of King Arthur, the Roman historian was taking a position about the present in projecting the religious arrangements of Rome back into the far past. They may, who knows have been founded much later, but by crediting them to Numa what Livy was doing, even if he was not recounting the facts, was demonstrating that these religious practices should be respected.
They had survived Tarquin and Brutus- they should survive Caesar and Brutus- and even Octavian.