You may remember from high school civics that the government is divided into legislative, executive, and judicial branches. Seems Aristotle taught the same thing, as chapters ⅹⅳ–ⅹⅵ of book Ⅳ of the Politics discuss each of these in turn.
Given this, you might make the case that (1) Aristotle was just right, this is how human governments naturally divide, and our governments today bear this out; (2) the influence of the tradition of political thinking that Aristotle represents on the subsequent development of politics and political thinking is so strong that today’s governments still bear its stamp…
…or (3) today’s governments aren’t really structured this way at all, but we still talk about them as though they were — emphasizing overt Aristotelean political institutions like Congress, the Presidency, and the Supreme Court, and downplaying the political power of institutions like the press, the universities, the bureaucracies, the military-industrial complex, the intelligence agencies, the banking/finance industry, think-tanks and lobbyists, the ultra-rich — because the influence of Aristotle’s tradition has so infused our way of talking about politics.
Be that as it may, Aristotle first discusses the legislative element in government. This, he says, has the following responsibilities:
- “decisions as to war and peace”
- “the making and dissolving of alliances”
- “the penalties of death, exile, and confiscation of goods”
- “the choosing of officials, and the scrutiny of their conduct on expiry of tenure”
The extent to which the citizenry as a whole exercise these powers or to which these powers are held by an exclusive body is a good way of determining the sort of government it is (e.g. oligarchical or democratic). Furthermore, even in governments in which the people as a whole control these powers, they may do so in different ways (for instance by taking turns in deliberative office, or by delegating certain decisions to appointed boards, or by insisting on putting everything up to a popular vote).
A legislature may also operate either within the limits of existing law, or may presume the right to be limited only by its own majoritarian decisions.
In democracies, Aristotle recommends the use of prods of some sort, such as payment for attendance for the poor and fines for non-attendance for the rich, to assure that there is a balance of representation of both groups in the legislature.
In oligarchies, on the other hand, Aristotle recommends that at least some members of the legislature be chosen from the common people, and that the legislature be limited to deliberating on proposals that have been pre-selected for them by an exclusive body (or perhaps that the legislature only be allowed to issue advisory opinions or vetos rather than edicts) so that they don’t use their power too broadly or outside of existing constitutional limits.