What is the necessary and proper clause? Why does the Constitution have a necessary and proper clause?

The Necessary and Proper clause was intended to allow Congress to decide whether, when and how to legislate for "carrying into execution" the powers of another branch, and at the same time intended to respect and reinforce the principle of separation of powers.

answer; i believe the answer is (mesopotamia); modern day

montesquieu took the view that the roman republic had powers separated so that no one could usurp complete power. in the british constitutional system, montesquieu discerned a separation of powers among the monarch, parliament, and the courts of law.