If we seek to define Roman unity a little more closely the following elements will be found perhaps the most important for our purpose. (1) It was a unity of government strongly centralized at Rome in the person of the emperor. The letters of a provincial governor like Pliny to his master Trajan at Rome reveal to us how even trivial matters, such as the formation of a guild of firemen in Pliny's province of Bithynia, were referred up to the emperor. Roman government was in fact personal and centralized in a very complete sense, and had the uniformity which accompanies such a condition. (2) This centralized personal government is, of course, only possible where there is a well-organized system of inter-communication between the widely-separated parts of a great {23} empire. And there was this to an amazing extent in the Roman empire. We find evidence of it in the great roads representing a highly developed system of travelling. 'It is not too much to say that travelling was more highly developed and the dividing power of distance was weaker under the Empire than at any time before or since until we come down to the present century.' This is what gives such a modern and cosmopolitan flavour to the lives of men of the Empire as unlike one another in other respects as Strabo and Jerome. We find the evidence of such a system of inter-communication also, and not less impressively, in the multiplied proofs afforded to us that every movement of thought in the Empire must needs pass to Rome and establish itself there. The rapid arrival of all oriental tendencies or beliefs at Rome was, of course, what from the point of view of conservative Romans meant the destruction of all that they valued in character and ideals. 'The Orontes had poured itself into the Tiber.' But it was none the less a fact of the utmost significance for the world's progress. (3) The unity of the Empire depended largely on the use which was made of Greek civilization and Greek language. The Empire {24} may be rightly described, if we are considering its eastern half, as Greek no less than Roman from the first. Everywhere it was the Greek language which was the instrument of Roman government, and Greek civilization, tempered by somewhat barbarous Roman 'games,' which was put into competition with local customs whether social or religious[16]. (4) Lastly, to a very real extent the Empire was aiming at the establishment of a universal religion. Independent local gods and local cults suited well enough a number of independent little tribes and kingdoms, but it was felt instinctively that the one empire involved also one religion, and with more or less of deliberate intention the one religion was provided in the worship of the emperor, or, perhaps we should say, of the Empire.