A.   Separation of powers has been an important part of democracy since the early Greek City-States, and was a central feature of the Roman Republic. George W. Bush and Dick Cheney have been doing their best to undo this founding principle of democracy for some time. They object to any congressional oversight of the executive branch, and have appointed Supreme Court judges who believe in a strong executive. We all know the endless stream of abuses which have taken place under the Bush White House, many of them posing serious threats to civil liberties. And yet, somehow, the basic building blocks of US democracy remain intact - barely. (source:  Separation of Powers--Kerim Friedman)

B.      The premise behind the Separation of Powers is that when a single person or group has a large amount of power, they can become dangerous to citizens. The Separation of Power is a method of removing the amount of power in any group's hands, making it more difficult to abuse.

The US government has a partial Separation of Powers. It distinguishes between three groups. The Executive, the Legislative, and the Judicial. They are distinguished by the kind of power they wield. The Legislative branch has the ability to enact laws. The Executive branch has the ability to see those laws enforced. The Judicial branch has the ability to decide the guilt of a party, allowing punishment.

If a single group shared all three powers, they would have unlimited power. They could specify any law, arresting the 'criminal', and then decide that they are guilty. Through the Separation of Powers, though, no group can have more than one of these powers. Only through the combined use of all three can the government use force. By requiring the consent of all three branches, it increases the likelihood that the government will not initiate violent force.  (source:  Jeff Landower and Joseph Rowlands--Separation of Powers)