This book discusses the philosophical underpinnings, constitutional provisions, and judicial application of the separation of powers doctrine. In the United States, the doctrine has evolved to ensure that there are three branches of government, each with its own function and each with an equal amount of power. This allows each branch, executive, legislative, and judicial to work efficiently and prevents the excessive accumulation of power by any single branch through a system of checks and balances. This book presents an overview of the rationale of the doctrine along with its application.