Final answer:
Glaucon ranks the regime types at 580b in Plato's Republic by their degree of injustice, with aristocracy as the most just and tyranny as the least just.
Step-by-step explanation:
At 580b in Plato's Republic, Glaucon ranks the regime types in order of the degree of injustice they exhibit. This ranking reflects the decline from the most just regime to the most unjust. Glaucon's ranking of regime types is not explicitly about their moral virtue, population size, or the pleasure they provide.
According to the dialogue, the aristocracy is considered the most just government, as it is ruled by philosopher-kings who possess both practical and theoretical knowledge, making decisions for the good of the community. This is followed by timocracy, a regime that values honor and military prowess, but begins to see the emergence of personal and societal vices like the pursuit of wealth. Next is oligarchy, characterized by a few ruling for their own benefit, with a focus on wealth and class division, leading to further injustice. Then comes democracy, which, despite its positive aspects, is seen as deviant because it could result in the tyranny of the majority, neglecting the common good. Lastly, tyranny is deemed the most unjust form of government, where the ruler is fully self-interested and imposes their will upon the citizens without regard for justice or the common good.
The evaluation of these regimes is part of the larger philosophical conversation on justice and the best political structure to ensure a virtuous city, a discussion that also engaged philosophers like Aristotle and Al-Farabi. Plato's ideal government is that of an aristocracy led by philosopher-kings, as depicted in his concept of the just city.