timelets

For kingship it is the system we have been calling tyranny, for aristocracy it is oligarchy, and for democracy it is government by brute force. According to the theory I have just outlined [from Plato's Republic], it is inevitable that each of these political systems will finally degenerate into its vicious counterpart.

As a precautionary measure, then, the constitution Lycurgus drew up was not simple and uniform. He bundled together all the merits and distinctive characteristics of the best systems of government, in order to prevent any of them growing beyond the point where it would degenerate into its congenital vice. He wanted the potency of each system to be counteracted by the others, so that nowhere would any of them tip the scales or outweigh the others for any length of time; he wanted the system to last for ever, maintained in a high degree of balance and equilibrium by the principle of reciprocity†. Kings were prevented from becoming overbearing by fear of the citizen body, who were assigned a fair share in government; the common citizens, in their turn, were deterred from disrespecting the kings by fear of the elders, all of whom were bound to cleave con- stantly to justice, because the criterion for selection for the Council of Elders was virtue. This meant that the part of the system that was at a disadvantage because of its conservatism* would always be reinforced and given added weight by the predilection and inclination of the elders. And the upshot was that the constitution so framed by Lycurgus preserved independence in Sparta longer than anywhere else in recorded history.

Lycurgus used calculation to predict how the nature of each of these systems of government would dictate its beginning and its out- come; he drew up his constitution without having suffered. But in the Romans’ case, even though the result was the same, in that they created the same kind of regime for themselves, this was not at all the outcome of reason, but of many struggles and trials.

...
There were three fundamental building blocks of the Roman constitution—that is, all three of the systems I mentioned above. Each of them was used so equitably and appropriately in the order- ing and arrangement of everything that even native Romans were hard put to say for sure whether their constitution was essentially aristocratic, democratic, or monarchic. This is not surprising: the constitution would have appeared monarchic (or a kingship), aristocratic, or democratic, depending on whether one focused attention on the powers of the consuls, the powers of the Senate, or the powers of the common people.

--- Polybius, The Histories.