Leviathan (Hobbes book)
Types

There are three (monarchy, aristocracy and democracy):

The difference of Commonwealths consisted in the difference of the sovereign, or the person representative of all and every one of the multitude. And because the sovereignty is either in one man, or in an assembly of more than one; and into that assembly either every man hath right to enter, or not every one, but certain men distinguished from the rest; it is manifest there can be but three kinds of Commonwealth. For the representative must needs be one man, or more; and if more, then it is the assembly of all, or but of a part. When the representative is one man, then is the Commonwealth a monarchy; when an assembly of all that will come together, then it is a democracy, or popular Commonwealth; when an assembly of a part only, then it is called an aristocracy.

And only three; since unlike Aristotle he does not sub-divide them into "good" and "deviant":

Other kind of Commonwealth there can be none: for either one, or more, or all, must have the sovereign power (which I have shown to be indivisible) entire. There be other names of government in the histories and books of policy; as tyranny and oligarchy; but they are not the names of other forms of government, but of the same forms misliked. For they that are discontented under monarchy call it tyranny; and they that are displeased with aristocracy call it oligarchy: so also, they which find themselves grieved under a democracy call it anarchy, which signifies want of government; and yet I think no man believes that want of government is any new kind of government: nor by the same reason ought they to believe that the government is of one kind when they like it, and another when they mislike it or are oppressed by the governors.

And monarchy is the best, on practical grounds:

The difference between these three kinds of Commonwealth consisteth not in the difference of power, but in the difference of convenience or aptitude to produce the peace and security of the people; for which end they were instituted. And to compare monarchy with the other two, we may observe: first, that whosoever beareth the person of the people, or is one of that assembly that bears it, beareth also his own natural person. And though he be careful in his politic person to procure the common interest, yet he is more, or no less, careful to procure the private good of himself, his family, kindred and friends; and for the most part, if the public interest chance to cross the private, he prefers the private: for the passions of men are commonly more potent than their reason. From whence it follows that where the public and private interest are most closely united, there is the public most advanced. Now in monarchy the private interest is the same with the public. The riches, power, and honour of a monarch arise only from the riches, strength, and reputation of his subjects. For no king can be rich, nor glorious, nor secure, whose subjects are either poor, or contemptible, or too weak through want, or dissension, to maintain a war against their enemies; whereas in a democracy, or aristocracy, the public prosperity confers not so much to the private fortune of one that is corrupt, or ambitious, as doth many times a perfidious advice, a treacherous action, or a civil war.
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