The sign was the Christian Cross, which gave victory, so he believed, to the Emperor Constantine in 312 CE, and began the establishment of Christianity as the official religion of the Roman empire. It was a conviction, in his case, halfway between the Classical notion of a father-god such as Jupiter, who presided over the natural order of the world and gave victory to his favourites, and the Biblical notion of a god with a message, who required a missionary to deliver it, a people to believe in it, and by extension, a statesman to institute it as the divine order of society. Under Constantine and his successors, it was the Biblical notion that prevailed. His victory over his rival for the throne began a new era in which belief in such a God and the truth of His scriptural commandments was established as the beginning and end of life and knowledge. As a principle of knowledge it imposed a new frame of reference on the wisdom of Greece and Rome to meet the new criteria of revelation. As a rule of life it became the prerequisite of government, with or without the state. For the latter it was a two-edged weapon. On the one hand it required obedience to the ruler on the authority of God; but on the other it measured his performance against the divine decree. In the first instance it was a formula for unanimity and submission, in the second a recipe for disagreement and opposition.