Final answer:
An aristocracy is a government run by a hereditary elite class, often based on noble lineage, while an oligarchy is a government in which a small group of people who have gained power through various means like wealth or military strength rule, without the necessity of hereditary succession.
Step-by-step explanation:
An aristocracy and an oligarchy are both forms of government where a small group holds the power, but they differ in the nature of this elite group. In an aristocracy, the ruling authority is usually hereditary, involving noble lineage or succession, where social status and family ties determine a person's proximity to power. In contrast, an oligarchy can consist of people who have gained their positions through various means, such as wealth, military power, or economic influence, rather than solely by birthright. Oligarchies do not necessarily operate within a framework of hereditary succession and can include a theocracy, where religious leaders hold sway.
For example, during the Archaic Age, Greek aristocrats were the 'best people,' arising from the wealthiest and most powerful citizens; their status often became hereditary over time. Oligarchic governments, however, manifest where few individuals, such as corporate executives or military leaders, control the society, sometimes even within political systems that claim to be democracies. Influential political analysts have even described modern democracies as being more akin to oligarchies where the elite ruling classes hold the power, rather than the majority of citizens.