Authority vs. Power: Political Philosophy and Human Nature
Authority and Power
Any state must be able to ensure that its laws are respected by the citizens. Without power, there is no authority.
Power is the ability to make things happen. It means getting people to do ones they would not otherwise do. This could be achieved by physical force, but more often knowledge is enough (of what power might do).
Nevertheless, power established by and relying exclusively on brute force can't last too long. When a political regime has to send tanks into the streets, it is usually the beginning of the end for them. The imposition of tyrannical force is not a safe prospect for the ruler in the long term.
The citizens need a positive reason for obeying. A sovereign who wants to last long usually offers people something...