How did Polybius describe the mixed constitution of the Roman Republic?

The Greek historian Polybius described the Roman Republic as possessing a "mixed constitution," which he believed was the key to the state's stability and success.12

According to his analysis, the Roman system successfully integrated three distinct elements of government:

• Monarchy: Represented by the magistrates.
• Aristocracy: Represented by the Senate.
• Democracy: Represented by the popular assemblies.

Polybius argued that, according to Greek political theory, simple forms of government were inherently unstable and prone to a cycle of decline and replacement. He believed that Rome’s system of balance acted as a check on this cycle, preventing the deterioration that typically plagued other states. While modern scholars note that Polybius likely exaggerated the symmetry of these checks and balances to fit his theoretical framework, his concept of the mixed constitution remained highly influential, shaping the political thought of figures from Cicero to Montesquieu.31