I quote from the Encyclopedia Britannica,

Aristotle used the term oligarchia to designate the rule of the few when it was exercised not by the best but by bad men unjustly. In this sense, oligarchy is a debased form of aristocracy, which denotes government by the few in which power is vested in the best individuals. Most classic oligarchies have resulted when governing elites were recruited exclusively from a ruling caste a hereditary social grouping that is set apart from the rest of society by religion, kinship, economic status, prestige, or even language. Such elites tend to exercise power in the interests of their own class.

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The authors are correct here to emphasize “rule by the few,” rule “not by the best men” and the claim that oligarchy is a “debased” or corrupt form of aristocracy, in Aristotle's Politics. As we will see, the usage of the term “oligarchy” has in recent times been often replaced by talk of “elites” --which essentially leaves open the question of whether these elites are good or bad, whether their rule is corrupt, or –importantly—whether they rule in the interest of the common good. For Aristotle, the aristocratic decline into oligarchy consists in "the few" ruling in their own narrow self interest.

Britannica continues:

It is a recurrent idea that all forms of government are in the final analysis reducible to the rule of a few. Oligarchs will secure effective control whether the formal authority is vested in the people, a monarch, the proletariat, or a dictator. Thus, Karl Marx and Friedrich Engels insisted that, throughout capitalism, the key capitalists had controlled the government; they coined the dictum, the state is the executive committee of the exploiting class. The Italian political scientist Gaetano Mosca likewise insisted that a ruling class always constituted the effective oligarchic control. Vilfredo Pareto elaborated the idea in his doctrine of the “elite.” The modern tendency to analyze social patterns in terms of an “elite,” although greatly reinforced by Pareto's theory, goes further back than Marx and Engels, who employed the term “elite” to describe the class-conscious communists, the leading group within the proletariat.

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Here we begin to come to the idea of the “Iron law of oligarchy,” or the “inevitability of oligarchy,” though this becomes more explicit in the passage below. The Marxist description of the elite communists as an oligarchy is interesting and ironic partly because oligarchy became the charge raised against the Communist system by Djilas, the Yugoslav dissident and critic in his classic book, The New Class. If oligarchy could survive even the socialist abolition of private ownership of the means of production, then, of course, this makes the claims for the “iron law” all the stronger.

Britannica continues:

One of the most famous modern uses of the term occurs in “iron law of oligarchy,” a concept devised by the German sociologist Robert Michels to refer to the alleged inevitable tendency of political parties and trade unions to become bureaucratized, centralized, and conservative. His reasoning was that, no matter how egalitarian or even radical the original ideology and goals of a party or union may be, there must emerge a limited group of leaders at the centre who can direct power efficiently, get things done through an administrative staff, and evolve some kind of rigorous order and ideology to ensure the survival of the organization when faced by internal division and external opposition. Subsequent writers of various persuasions have attempted either to expand on Michels' thesis, extending it to legislatures, religious orders, and other organizations, or to restrict or criticize the thesis, charging that the iron law of oligarchy is not universal and that some unions and parties do maintain a viable system of democratic expression and governance.

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If the “iron law” fails, then it must be the case that oligarchy is not inevitable under just any conditions, or in all situations. What then are the facilitating conditions and what kinds of conditions tend to defeat the rule or control of oligarchy?

Britannica continues:

Political science and sociology are beginning to differentiate more carefully between various types of control and power. The type of power held by a democratic party boss, while overwhelming in relation to any single member of the party, is very different from that wielded by the boss of the single party in a totalitarian and authoritarian pattern. Likewise, the control group within an organization does not occupy the same position under democratic conditions (which provide for the group's being effectively challenged by outsiders at any time) as it does under an authoritarian plan. If effective control changes hands as rapidly as it does in a city of the United States or a British trade union, it is doubtful that those exercising it should be spoken of as a “class” or an “elite.” The expression “the few” is too abstract to convey much information. Like the other purely numerical concepts of government inherited from Greek philosophy, oligarchy is an outmoded term, because it fails to direct attention to the substantive features of a government.

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Well, if the term “oligarchy” is outmoded, it is somewhat surprising that the political scientists have begun to use near synonyms, such as “biased pluralism” --with the bias typically favoring the upper incomes. Again, there is “economic elite domination,” also quite current, which suggests in turn the theme of “policy capture,” and the domination of economic and tax policy by large-scale institutions and great wealth. No doubt, we want to distinguish between political control, kinds and conditions of political control --and with special attention to the reasonable prospect of a given ruling-set being turned out. The term, ”rule by the few” is indeed too abstract to capture even the concept of oligarchy. It is more a matter of “rule by the few”-- in their own self-interest, and ignoring the common good. Oligarchy is not merely numerical, it is also a moral and political concept –which can't be reduced to numbers alone.

See: the Britannica article, here: https://www.britannica.com/topic/oligarchy

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