What was wrong with the republican model for eighteenth century thinkers about liberty, if they themselves have sometimes been taken up as republican, or at least partly republican, thinkers? The answer can be summarised with reference to a city state where Rousseau himself spent time as a secretary to the French ambassador, Venice. Those looking for an example of a modern republic in the eighteenth century were likely to look at Venice. Another possible example was the Dutch Republic, but at least for Montesquieu (who I will take it was not deviating far from any prevailing judgement) it was a more a confederation of city republics which struggled to achieve unity in times of danger. By the eighteenth century the glory of the Golden Age, of Rembrandt and Spinoza, of recent independence after a long war from Spain, of a model of financial and commercial progress, was in the past, and no one thought of the Dutch Republic as a major European power.
Furthermore its relative youth, going back no further than the 1560s, mattered to eighteenth century thinkers who though that successful model states are states that maintain themselves over centuries, preferably with a largely unchanged constitution. That Athens had only a couple of centuries maybe as an independent and democratic republic was important compared with the much longer life of Sparta’s oligarchic republic. That Roman republicanism gave way to a thinly disguised version of monarchy in the Emperor system after five centuries mattered, as did the apparent weakening of republicanism and democratic life after the defeat of Carthage.
Two centuries of republican life in the United Provinces was small compared with about one thousand years of the Venetian Republic, which like the Dutch Republic was past its greatest period of influence, but could be taken as more of a model with an apparently little changed constitution over a long life by the standard of any European state. By the tine of Enlightenment political writing Venice was a museum of a glorious past as a dominant commercial and naval power, with an eastern Mediterranean empire. Montesquieu comments unfavourably on a constitution which he thought allowed the aristocracy to act as government executive, legislator, and judiciary, with the special powers of secret committees to defend the state undermining liberty.
His criticism is more than justified by the greatest Italian witness of the time, Giambattista Vico (whose thought anticipates much in Rousseau and Montesquieu). Vico thought of Venice as the model of aristocratic republic in which the aristocracy regards itself as more than human and the common people as less than human. It precedes the situation in which democracy encourages the spread of an idea of a common humanity, an idea that Vico thought could only maintain itself through democracy giving way to a human monarchy, legislating and judging with regard to the welfare of all.
I do not think that Vico ever says these things about Venice directly, but his view of the formation of the first states, is that we can understand them as ruled by Homeric warrior-heroes, that is an aristocracy that considers itself to be godly. His description of how such a state emerges in the New Science clearly draws on the history of Venice in the Middle Ages, a period which Vico regarded as the repetition of ancient barbarism.It is widely believed that the city of Venice emerged in the ‘barbarian’ invasions of the Roman west as a place where refugees fled in lagoons where the invading armies did not go. The first refugees formed a community in territory which became the privileged class when later refugees and migrants came, who formed the lower class with lesser rights under the older now aristocratic community. The history of Venice as an independent city republic comes from an eighth century separation from Constantinople. The period before that is the model for Vico of how ancient city states, were created, particularly Rome, which is widely believed to have been open to refugees and migrants from early times.
By the early eighteenth century republicanism has come to mean for one major thinker a state where some element of Homeric society remains as opposed to great monarchical states where increasingly some spirt of equality under law and union through trade can be discerned, even if imperfectly executed. This is not the final word for Enlightenment views of republics, but it does show something about why the major Enlightenment thinkers were not anticipating a glorious new dawn of European republicanism.