Division of power within the government was put forth in

 The Spirit of the Laws

The concept of the division of power within a government, which is also known as the Separation of Powers, was proposed by the French philosopher Baron de Montesquieu in his influential work The Spirit of the Laws (1748). Montesquieu's theory is based on the idea that in order to prevent any one branch of government from becoming too powerful and to protect individual liberty, governmental power should be divided into three distinct branches:

1. The Executive: This branch is responsible for enforcing laws and managing the affairs of the state.
2. The Legislature: This branch is responsible for making laws.
3. The Judiciary: This branch interprets and applies the laws.

Montesquieu argued that by separating powers and ensuring checks and balances, each branch would be able to monitor and limit the actions of the others, thereby preventing the abuse of power. This division of powers has been a fundamental concept in modern democracies, including the structure of governments in countries like the United States, India, and many others.