The strongest is never strong enough to be master all the time, unless he transforms force into right and obedience into duty.
Gist of Idea
Force can only dominate if it is seen as a right, and obedience as a duty
Jean-Jacques Rousseau (The Social Contract (tr Cress) , I.3)
Presumably the people only accept force as a right and obedience as a duty if they appear to be in the people's interests - because the alternative looks worse. In other words, they are terrified.
Rousseau,Jean-Jacques: 'The Basic Political Writings', ed/tr. Cress,Donald A. [Hackett 1987], p.143