Full Idea
The Federalists took the idea of 'separation of powers' from Locke and Montesquieu. This places the legislative, executive and judicial functions in independent hands, so that in theory any branch of government would be checked by the other two.
Gist of Idea
'Separation of powers' allows legislative, executive and judicial functions to monitor one another
Source
Jonathan Wolff (An Introduction to Political Philosophy (Rev) [2006], 3 'Representative')
Book Reference
Wolff,Jonathan: 'An Introduction to Political Philosophy (Rev)' [OUP 2006], p.96
A Reaction
[The American Federalist writers of 1787-8 were Madison, Hamilton and Jay] This is a brilliant idea. An interesting further element that has been added to it is the monitoring by a free press, presumably because the other three were negligent.