once been ruled by Etruscan kings. Mystery religions imported from the Near East (Ptolemaic Egypt, Persia and Mesopotamia), which offered initiates salvation through a personal God and eternal life after the death, were a matter of personal choice for an individual, practiced in addition to carrying on one's family rites and participating in public religion. The mysteries, however, involved exclusive oaths and secrecy, conditions that conservative Romans viewed with suspicion as characteristic of "magic", conspiracy (coniuratio), and subversive activity. Sporadic and sometimes brutal attempts were made to suppress religionists who seemed to threaten traditional Roman morality and unity, as with the Senate's efforts to restrict the Bacchanals in 186 BC. As the Romans extended their dominance throughout the Mediterranean world, their policy in general was to absorb the deities and cults of other peoples rather than try to eradicate them, since they believed that preserving tradition promoted social stability. One way that Rome incorporated diverse peoples was by supporting their religious heritage, building temples to local deities that framed their theology within the hierarchy of Roman religion. Inscriptions throughout the Empire record the side-by-side worship of local and Roman deities, including dedications made by Romans to local Gods. By the height of the Empire, numerous international deities were cultivated at Rome and had been carried to even the most remote provinces (among them Cybele, Isis, Osiris, Serapis, Epona), and Gods of solar monism such as Mithras and Sol Invictus, found as far north as Roman Britain. Because Romans had never been obligated to cultivate one deity or one cult only, religious tolerance was not an issue in the sense that it is for competing monotheistic religions. The monotheistic rigor of Judaism posed difficulties for Roman policy that led at times to compromise and the granting of special exemptions, but sometimes to intractable conflict. Christianity Some Christians have argued that religious pluralism is an invalid or self-contradictory concept. Maximal forms of religious pluralism claim that all religions are equally true, or that one religion can be true for some and another for others. Most Christians hold this idea to be logically impossible from the principle of contradiction. The two largest Christian branches, the Catholic Church and the Eastern Orthodox Church, both claim to be the "one true church" and that "outside the true Church there is no salvation"; Protestantism however, which has many different denominations, has no consistent doctrine in this