Below is a quote from James Madison’s Federalist Paper No. 51 (1788): “if men were angels, no 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.”
James Madison, Federalist Paper No. 51 (1788)

To which fundamental principle is Madison referring?