The 2nd century historian Polybius (200 – 118 BC), in the sixth book of his Histories, writes about the efficiency of the Roman polity. For this purpose, he makes comparisons with older Greek polities.
In excerpt 6.43 he writes that Thebes’ successes were not owed to its polity, but to Epaminondas and Pelopidas, as the power and the flourishing of the city came and went along with them. Here, you can read excerpt 6.44:
“We must hold very much the same opinion about the Athenian constitution. For Athens also, though she perhaps enjoyed more frequent periods of success, after her most glorious one of all which was coeval with the excellent administration of Themistocles, rapidly experienced a complete reverse of fortune owing to the inconstancy of her nature. For the Athenian populace always more or less resembles a ship without a commander. In such a ship when fear of the billows or the danger of a storm induces the mariners to be sensible and attend to the orders of the skipper, they do their duty admirably. But when they grow over-confident and begin to entertain contempt for their superiors and to quarrel with each other, as they are no longer all of the same way of thinking, then with some of them determined to continue the voyage, and others putting pressure on the skipper to anchor, with some letting out the sheets and others preventing them and ordering the sails to be taken in, not only does the spectacle strike anyone who watches it as disgraceful owing to their disagreement and contention, but the position of affairs is a source of actual danger to the rest of those on board; so that often after escaping from the perils of the widest seas and fiercest storms they are shipwrecked in harbor and when close to the shore. This is what has more than once befallen the Athenian state. After having averted the greatest and most terrible dangers owing to the high qualities of the people and their leaders, it has come to grief at times by sheer heedlessness and unreasonableness in seasons of unclouded tranquility. Therefore I need say no more about this constitution or that of Thebes, states in which everything is managed by the uncurbed impulse of a mob in the one case exceptionally headstrong and ill-tempered and in the other brought up in an atmosphere of violence and passion.”
Polybius goes on to compare the polities of Crete and Sparta. Since, in Crete, “no gain is disgraceful”(6.46), the citizens have a tendency towards profiteering and avarice. Lycurgus of Sparta, though, by removing avarice, he has removed along with it any discord and variance. He did this by combining the best things that all the differing polities have to offer, so that the city would not bend too much towards one or the other (kingship, aristocracy, democracy) and, thus, turning into a deviation of them (monarchy/tyranny, oligarchy, ochlocracy), as the city augments in size more than it should. The Romans, on the other hand, Polybius says, managed the same result, not by using reason, but through much struggle and hardship, choosing the best things from each polity by using the insights they had gathered through their endeavors.
You can find the original here.