The thesis that luxury had destroyed ancient European civilization actually originated from the ancients themselves, who were capable of formulating the best theoretical accounts of their own demise. This was not an explanation after the event, it was a prediction that had come out true. Whatever the problem with ancient societies, it was not their lack of theoretical understanding. Their problem was not actually with theory but with practice...Ultimately they went down altogether, while still remaining fully aware of their mistake...According to Rousseau...[t]he ancient failure was not because the theory was false but because the ancients did not follow their theory in practice. Istvan Hont Politics in a Commercial Society, 89-90. [In context, Hont is describing Rousseau's response to the so-called 'luxury debate' (recall yesterday's post.)]
According to Hont's analysis, Rousseau is not describing a self-fulfilling prophecy, which is, according to Merton, "in the beginning, a false definition of the situation evoking a new behavior which makes the original false conception come true. This specious validity of the self-fulfilling prophecy perpetuates a reign of error." (Only if Rousseau's social theory were false, then it could be possible that the ancients suffered the consequences from a self-fulling prophecy.) I mention a self-fulfilling prophecy because it can generate a species of practical impotence; if one does not stop the effects/impacts of a self-fulfilling prophecy early enough (i.e., when it's description is still false-ish), then it becomes nearly impossible (i.e., once its description is true).
Rousseau is also not describing a species of fatalism, that is, "the view that we are powerless to do anything other than what we actually do." By Rousseau's lights (a) the ancients could have done otherwise [in some sense], and (b) they believed they could do otherwise. (Again, this is not to rule out the possibility that Rousseau is wrong about (a) or (b).) According to Omri Boehm's reception of Spinozistic fatalism (recall), fatalism naturally slides into nihilism (which is indeed a plausible disposition accompany a species of practical impotence.) On (b): the ancients articulated their theoretical knowledge in order to change a foreseeable, but not inevitable outcome. On (a): reflection on Rousseau's recipe for change (build new institutions and habits in which a society can act on knowledge) in light of ancient experience (and his social theory), suggests that the nature of 'this could have done otherwise' is a bit tricky given their institutions and practices.
So, Rousseau is describing a kind of social akrasia (from the Greek ἀκρασία), that is, the possibility of a society acting against its better judgment and, thereby, demising. (A mortal collective action problem, as it were.) Of course, -- unless one is an economist who thinks all revealed behavior just is optimal, that is, with a tacit belief in theodicy -- non-lethal forms of social akrasia are not un-common (which is why I specified the 'demise' part)--fill in your favorite examples (American sugar subsidies, Dutch housing policy, etc.). To be clear, not all societies always value (earthly) survival; so if people are knowingly willing to die for a way of life (a God, a culture, philosophy, etc.) then, even if outsiders find their behavior delusional or akratic, it does not count as social akrasia. Obviously, there are complex cases where societies are in denial about the truth (or their good) -- say, during war fever, or bubble economies -- which may count as akratic, despite, perhaps, not meeting the standards of the definition.
Now it's easy to take for granted that the presence of certain institutions will prevent (excessive) social akrasia: modern (and independent) science, free speech/press, accountable and replaceable government, educated elites, and, even, knowledge about how to tackle collective action problems. But what makes the case(s) contemplated by Rousseau so interesting, is that he is describing (oligarchic) societies where the political, economic, and intellectual elites overlap greatly. So, where social akrasia is not caused by a kind of disunity among rulers, but rather by mistaken, downright foolish behavior.*
Only a fool will assume that purportedly advanced or developed (or civilized) societies cannot act foolishly.