It is usually said that the modern state, with its centralized administrative apparatus and uniform system of justice, is only around half a millennium old. This is certainly true in the west.
However, throughout what westerners call the middle ages the remnant of the Roman Empire centred in Constantinople maintained something reminiscent of the modern state in the territories under its rule. This can be seen in a fascinating article by Angeliki E. Laiou, "Byzantium and the West." In this article she has two fictional men from France and Venice respectively, Hugh and Paolo, travelling to Constantinople in the late 12th century and observing the differences from what they are accustomed to at home:
Here Hugh would have come up against a first astonishing experience, that is, the existence of a representative of the central government, functioning as such, in a place remote from the capital. Such an experience could not have been duplicated in any other European state. At the time, in France the effective power of the Capetian king was still limited to his own domains, certainly not extending to Champagne, even though he was the suzerain of the count, Henry the Liberal. The very fact of the existence of a large and relatively unified state would have been something to wonder at. On the way, Hugh would have seen to his astonishment that important aspects of government which in France were in the hands of the feudal nobility were here clearly in the control of the state, and therefore uniform. He must have been surprised that there was no diversity of weights and measures. More importantly, he would have noted the existence of a single currency, issued by the imperial mint, at a time when his own kings were just beginning the long effort to recapture the monopoly of coinage. He might have compared the gold Byzantine coin to the small, silver, and still relatively scanty coins of Champagne. He could not but have been struck by the fact that there were no private castles, which could become strongholds of aristocratic opposition to the government, and that traveling was relatively safe.
I cannot help thinking of Herman Dooyeweerd's definition of the state as the community created by the government's monopoly of coercive swordpower over a defined territory. To this extent the Byzantine Empire appears to anticipate the rise of the state.
However, lest we wax too enthusiastic over the Byzantine political model, we should recall that it was in the west, where the nobility and the clergy possessed their own power bases distinct from the monarchy, that constitutional and representative government arose. The post-Byzantine east has had a more difficult time transcending the ancient political culture of monarchical absolutism which has effectively retarded the growth of democracy.
Thus the uniformity in the administration of justice in the Byzantine Empire was definitely advantageous compared to western feudal fragmentation, but the balance of competing estates in the west was over the long term more conducive to the development of constitutional government.
This autumn I plan to have my students in ancient and mediaeval political theory read Laiou's article.