The idea that the powers of government should be separated and balanced against each other; this should prevent any one person or government branch from gaining too much power and overcoming others ( by a system of checks & balances); Montesquieu is the one who gave us the 3 branches of government system.
Explanation:
Montesquieu's theory of separation of powers, on which most modern Western States are based, affirms the distinction between the three powers (executive, legislative and judicial) and their mutual limitations. For example, in a parliamentary democracy, the legislators (Parliament) limits the power of the executive (government): it is not free to act at will and must constantly secure the support of Parliament, which is the expression of the will of the people. In the same way, the judiciary allows counterbalancing certain governmental decisions.