Men's minds fell sick as well as their bodies; they became possessed by all sorts of superstitions, mostly of foreign origin, and the sort of people who can turn other men's superstitious terrors to their own advantage set up as seers and introduced strange rites and ceremonies into private houses, until the debased state of the national conscience came to the notice of the leaders of soicety who could not but be aware in every street and chapel of the weird and outlandish forms of new prayer by which their hag-ridden compatriots sought to appease the wrath of heaven. Then the government stepped in, and the aediles were instructed to see that only Roman gods were worshipped and only in the traditional way. (IV 30)
This passage within Livy's history demonstrates two central truths which dominated the history of Roman religion. The first is that Roman religion was influenced from abroad- who knows what 'foreign' customs Livy is talking about here. Influences came to Rome from Etrusca- where for instance the custom of lictors proceeding before Kings came in and some of the other 'Roman' customs arrived from. Many religious customs in Rome- the Sibylene prophesies for example- have even their professed origins as coming from abroad. It does not seem extraordinary to me to see that Rome borrowed and was borrowed from in a commerce of religious ideas that went throughout the Italian peninsular following the paths of trade and war. Of course the paths led south as well as north- we find the Romans borrowing Greek customs too. The story of Romulus and Remus has its antecedents in Greek myth- and even the entire idea of various Roman Gods- Apollo most importantly- came early and from Greece (according to Professor Burket at least.) This trend carried on through Roman history- the cults of Isis (Egyptian), Mithras (Syrian), Christ (Palestinian) and many others remain visible in the historical record to demonstrate to us the cosmopolitan nature of Roman religion: it is even visible in the worship of the Emperors themselves- a process that Tacitus tells us started in the Eastern Provinces and then came to the Imperial city.
Alongside this continuous process of religious adoptation of the ideas of others- and the adoptation might be philosophical too witness the Stoics- the Romans felt a deep anxiety about the corruption that these cults introduced. This passage reflects that anxiety. In particular Romans suggested that adopting the new Gods might lead the citizens to abandon the old ones who had served Rome well. Such new rites could often have a distabilising effect on individual lives- akin say to the fear about scientology today- an ancient Roman might see the Orphic cults of Greece as promoting sin, moral decay and leading young men and women astray. Livy's language with its warnings about the exploitation of the superstitious by those who set themselves up as 'seers' comes from that tradition. But the broader anxiety was focussed upon the very nature of the Roman republic- when Rome absorbed all these customs and ideas from abroad, how Roman did Rome remain? But this cultural mix flowed from Rome's engagement with and importance in patterns of trade and warfare that it wished to dominate- in which case without this fertilisation from abroad, the Republic risked becoming static and ultimately declining.
This tension at the heart of Roman history lies at the heart of Livy's history, it is a tension familiar to all imperial states. The tension lies between the idea of the imperial heartland and its importance as a centre- and the fact that in order to continue to govern its territories successfully, it has to absorb, observe and ultimately sympathise with them. Rome's destiny as an imperial state was eventually to sublimate the history of the city within the history of the empire- that is the heart of the revolution that Livy did not see- wherein the principate changed to an imperium- but Livy was already aware that Rome itself was becoming less Roman in his own day and that it had made its way in the world through adoptation and expropriation rather than purity. The Aediles stepped in to make sure Roman gods were worshipped alone- but how did they tell which were the Roman Gods (afterall almost all would have been influenced by foreign customs) and furthermore they were evidently not successful, as Rome was.
Machiavelli once said, commenting on Livy, that Rome as a republic forsook stability for expansion- the passage aboves testifies that this was a conflict that was alive in the minds of Romans like Livy- even if it was resolved in favour of expansion eventually.