The most important of these propositions are those which assert that there is an intimate connexion between the form of a political body and the form of government by which it is ruled: and that each of the forms that a political body can assume has a certain type or certain types of government commonly and almost uniformly associated with it. The propositions may be set down in the following way. Firstly, all the tribes of which we have any good records have had governments not differing from one another in any important particular. Secondly, cities pure and simple or inexpansive cities have usually three kinds of government only, pure oligarchy, or pure despotism, or direct and almost unmixed democracy: and Republican Rome, the single example of an expanded city, had a government peculiar to itself. Thirdly, in the large unitary states or nations, it is, roughly speaking, true that three kinds of government have succeeded one another in regular sequence: at first, during the middle ages, they were under governments in which power belonged partly to a king and partly to an assembly of estates, the assembly consisting usually of the nobles, the prelates of the church, and representatives from rural districts and towns: afterwards, when they were in danger of disruption, they placed themselves under monarchies of unlimited or almost unlimited power, and these monarchies usually continued to exist after all danger of disruption had been removed: and now, in modern times, all unitary states are ruled by cabinets under the control or supervision of popular representative assemblies. Turning to federal states, which form the fourth class of political communities, we find that all of them are alike in having a central government both legislative and executive, whose sphere of action is strictly limited by the constitution to certain portions of the work of governing, and in permitting each of the states, which are joined together in the federation, also to have a government of its own, which controls all business except that portion which is allotted by the constitution to the central government of the federation. And, lastly, heterogeneous empires must, unless they are to break in pieces, have governments whose chief object is centralisation. Supreme power may belong to a despotic monarch or to a small body of men appointed by a foreign state which rules the empire: but in all cases the one thing necessary is that there shall be a central supreme power and that the commands of that supreme power shall be implicitly obeyed by everyone within the empire.