The best for most cities
Mixed government is Aristotle's most practical political recommendation — the constitution he judges best, not in the abstract, but for most cities most of the time. The platform reads it as his characteristic move from the ideal to the achievable: rather than ask which regime is best simply (he allows that a truly outstanding ruler or aristocracy would be), he asks which regime ordinary cities, with ordinary citizens, can actually sustain — and answers, the polity (politeia in its narrow sense), a constitution that mixes oligarchic and democratic elements into a stable, moderate whole.
The logic of the mixture
The platform reads the logic of mixed government as the logic of balance. Pure oligarchy (rule of the rich for the rich) and pure democracy (rule of the poor for the poor) are each unstable, because each excludes and antagonizes a large part of the city, breeding the faction that destroys constitutions. Mixing the two — combining democratic institutions (election, broad participation) with oligarchic ones (property qualifications, deliberative councils) so that each element checks the other and neither dominates — produces a constitution in which more citizens have a stake and fewer have a grievance. The platform reads this under constitutional government: the mixed regime is stable because it is inclusive enough to bind its citizens to it.
The middle class
The platform reads Aristotle's most original contribution as the role of the middle class. A constitution is most stable, he argues, when the middling citizens — neither rich nor poor — are numerous and strong, because they are the natural moderators of the city: less prone to the arrogance of the rich and the envy of the poor, more amenable to reason and to the rule of law, and a buffer between the two extremes whose conflict tears cities apart. The platform reads this as one of the most durable insights in political science — that political stability rests on a broad middle — an insight rediscovered by every later analyst of constitutional health.
Why it matters for Virtue & Power
Mixed government is Aristotle's bridge between the realistic study of constitutions and the practical art of preserving them, and the root of the long Western tradition of balanced government that runs through Polybius and Cicero to the framers of modern constitutions. The platform reads it as one of the most influential and most practical of all classical political ideas, and central to Aristotle and constitutional government.