You must first enable the government to control the governed; and in the next place oblige it to control itself

From The Federalist No. 51, The Structure of the Government Must Furnish the Proper Checks and Balances Between the Different Departments, Wednesday, February 6, 1788 by James Madison.

If men were angels, no government would be necessary. If angels were to govern men, neither external nor internal controls on government would be necessary. In framing a government which is to be administered by men over men, the great difficulty lies in this: you must first enable the government to control the governed; and in the next place oblige it to control itself.

I see the first half of the quotation frequently cited but the second half much less often. Yet the second half of the quotation is the heart of the dilemma that needs addressing. Our entire Constitution is designed to address that quandary.