The need for a complete separation of the three branches of the state in relation to functions, bodies and personnel.
Some overlap of functions between the bodies so as to create checks and balances powers within the constitution. The theory suggests that this will reduce the ability of one body to have total freedom to operate without reference to another body.
'The threefold division of labour between a legislator, an administrative official, and an independent judge, is a necessary condition for the rule of law in modern society and therefore for democratic government itself.'
'The essence, though not the whole, of separation of powers lies in the meeting of form and function; the matching of tasks to those bodies best suited to execute them. The core of the doctrine is not liberty, as many writers have assumed, but efficiency...'