Why did Montesquieu warn against placing all political power in the same hands?

Montesquieu warned against concentrating all political power in the same hands because he identified the accumulation of such authority as the defining characteristic of tyranny.1

In his seminal work, The Spirit of Laws, he argued that the primary purpose of political association is the preservation of liberty. To safeguard this liberty, he proposed the separation of powers, asserting that the legislative, executive, and judicial functions of government must be entrusted to separate and independent bodies.123

By dividing these powers, Montesquieu sought to prevent arbitrary excesses by the state. This doctrine ensures that no single individual or institution possesses absolute control, as the cooperation of different branches is required to make, execute, and administer laws. This framework serves as a vital check against the human tendency toward tyranny, thereby protecting the dignity and freedom of individuals.3124