I have long been fascinated by Socrates's account of the fall of the luxurious city (developed between 372e-451b). About that soon. It is introduced with two laws: one is law in political science, the other is a law in metaphysics (although I note a complication below). First, Socrates notes:
[T]he simple and unvarying rule, that in every form of government revolution takes its start from the ruling class itself, when dissension arises in that, but so long as it is at one with itself, however small it be, innovation is impossible--Plato, Republic, 545d.
This law states, that all other things being equal, the power that allows an elite (of whatever kind) to rule at T1 is sufficient to allow it to rule at T1+n. So, that when elite unity is maintained, elite rule is maintained. (That is just to say, that elite rule is sufficient for bare political unity.) Obviously, other things are not always equal: sometimes a city is conquered or undermined from abroad. This would not refute the law. But sometimes the internal balance of power of a state also shifts and that may be thought, in contradistinction to the law, to generate the causes that allow for constitutional innovation or revolution. But I take Socrates's point to be that a unified and determined elite keeps a careful watch out against such shifts of power and decisively (appealing, say, to precautionary principles) acts against them in an anticipatory fashion.
I am not sure what the exact empirical status of Socrates's claim is, but history provides plenty of examples in which political revolutions are at least facilitated by elite defections. Of course, such elite disunity may may not so be the cause of decline in power as a symptom of it (as Socrates's subsequent examples also suggest).
The second law is a law of metaphysics:
Since for everything that has come into being destruction is appointed, not even such a fabric as this will abide for all time, but it shall surely be dissolved,--Plato, Republic, 546a.
We may say that this is the law of natural necessity (of the sort that all men are mortal, which is an instantiation of the law of metaphysics). The law covers the sensible world of matter in which, as the PSR teaches, everything has a cause, but in which everything has to perish, too.* That's to say, according to Socrates no principle of unity of a created thing is eternal. If we put the two laws together, we get (if we leave aside a complication I'll explain below) the following ruling principle of Socratic political metaphysics:
- As long as a political principle of a state's unity (that is the elite) remains unified a state's unity (and, thereby, its political order) persists, but no such principle of unity is eternal and, therefore, no state is eternal.
The complication is that the second law above is articulated by Socrates in his imitation of Homeric poetry (545d). Whatever else this shows, it proves that according to Socrates, poets can be made to sound like metaphysicians (recall José A. Benardete on Quine and the quarrel between philosophy and poetry).+ But here I'll pretend the complication does not undermine the status of the second law as well as the ruling principle.
Despite it relying on natural necessity, the ruling principle of Socratic political metaphysics is by no means obvious (despite it being an extremely solid empirical generalization). By this I do not just mean that both Aristotle, who seemed to think that a good mixture would really endure (see Politics 5), as well as Spinoza, who (in E3p6) articulated his Conatus doctrine against it (viz. "everything, in so far as it is in itself, endeavours to persist in its own being,"), reject it. Rather, I mean to call attention to the fact that the modern doctrine of open-ended progress, which may well owe something to this mixture of Aristotle and Spinoza, leaves little room for our demise. Even known civil war within liberal democracies (UK 1688; US 1861-5; Paris 1871; Spain 1936-9) are turned into glitches on the path toward true progress. [We might say that whenever the march of progress produces (a Vico or) a Spengler, a Toynbee and an Adorno await to rekindle faith in progress.]
Our current science teaches that one day our Sun will die and that one day in a remoter future the universe will be inhospitable to life as we know it. So, it is unlikely that open-ended progress is really true. The previous sentence used to be 'merely academic.' But with increasing odds of the reality of anthropic-induced ecological disaster, the continuing vitality of the ruling principle of Socratic political metaphysics is to be tested afresh in the next century or two.
*In Plato this also generates a cycle of eternal return, but about that some other time.
+The exchange with Glaucon reveals Glaucon's preference for poetry over more sober forms of philosophy.