Aristotle's political philosophy is consistent with his metaphysics. His metaphysics is based on a philosophy of nature that can be extended to social bodies. Aristotle's view of nature starts with an interpretation of causality, because he wants to create a framework that would help him to explain change and motion. Aristotle distinguishes four ways in which we respond to the why? question: We can point to the material cause (what something is made of), the formal cause (its definition, the idea that is embodied in it), the efficient cause (how it was created) and the final cause (the reason for which it was created.) This view of causality implies an ethics built into nature: things are good when they are created or built well and serve their natural purposes. Aristotle's philosophy of nature can easily be applied to human societies as well, and it results in a political theory that has withstood the test of time.
The notion of final cause dominates Aristotle's "Politics" from the opening lines: "Since we see that every city-state is a sort of community and that every community is established for the sake of some good (for everyone does everything for the sake of what they believe to be good), it is clear that every community aims at some good, and the community which has the most authority of all and includes all the others aims highest, that is, at the good with the most authority. This is what is called the city-state or political community. [Politics Book I.1.1252a1–7]
He also states in the opening chapters that the city-state comes into being for "the sake of life but exists for the sake of the good life." The theme that the good life or happiness is the proper end of the city-state recurs throughout this foundational text of Western Political Philosophy.
The state is a community (koinônia), a collection of elements that have some functions and interests in common. If we apply Aristotle's theory of causation to the existence of political units like States, it is evident that the State is composed as a "hylemorphism," a matter-form compound, and the following scheme emerges:
The material cause of the state is the population that lives in a given geographic territory.
It formal cause is the political constitution itself, the set of rules that governs the political unit. By "Constitution" Aristotle does not necessarily mean a written document, but mostly the immanent organizing principle, analogous to the “the way of life” of the citizens.
The efficient cause exists in the actual political process of creating and maintaining the state: the activities of lawmakers, politicians, parliaments, governance bodies, and rulers who are the craftsmen of the political trade.
Final Cause: The aim of the city-state, defined by the constitution.
Aristotle's political theory follows from his metaphysics that explains nature through its internal principle of motion and rest (Aristotle, Physics, Book III.1.192b8–15). Human societies emerge as natural entities that unleash human potential. He makes four claims about nature and the city-state:
The city-state exists by nature, because it emerges from the more primitive natural associations between people (couples, families, tribes) and it serves as their end goal, because the state is the functional social unit that attains self-sufficiency.
Human beings are by nature "political animals," because nature has equipped them with speech and enabled them to communicate and discuss moral concepts such as justice, which are formative of the household and city-state.
The city-state is naturally prior to the individuals, because individuals are not self-sufficient, they cannot function apart from the State.
Even though the State is natural, it is also a creation of human intelligence. “Therefore, everyone naturally has the impulse for such a [political] community, but the person who first established [it] is the cause of very great benefits.” The creators of the constitution deserve credit, they are the lawgivers (nomothetês). Without the legal system of the city-state, humans beings would not be just and virtuous; the state is the condition that lifts them from the savagery and bestiality in which they would otherwise exist.
Aristotle uses the term "nature" in a vague and somewhat undefined sense. States are not entirely natural, otherwise they would be beehives or ant colonies. Applied to humans, who are by nature intelligent, the State can become a product of culture: the law givers, or the sovereign, turn the natural potential in humans into the artificially created system of the State that develops through history.
The Aristotelian view of politics is based on the following assumptions:
Teleology: Aristotle opens the book on Politics by invoking the concept of nature. Nature organizes itself through final causes, or natural teleology: the nature of a thing is determined above all through its end or final cause, which also intrinsically determines the direction of development or movement.
Principle of perfection: Natural teleology leads to a natural ethics, because good and bad can be understood in terms of the realization of the intrinsic purpose of something. Achieving the natural purpose of the organism or the social unit is good for it, and what defeats or impedes this goal is bad.
Community: Aristotle maintains that the State is the most complete community, because it attains the goal of self-sufficiency, and it can then exist for the sake of the good life. Individuals outside of these social units are not self-sufficient, because they depend on the community not only for material necessities but also for their education and moral rectitude. “Just as, when perfected, a human is the best of animals, so also when separated from law and justice, he is the worst of all.” (Politics, 1253a31–3). Human beings must be subject to the authority of the State in order to attain the good life.
Leadership: Aristotle believes that the existence and well-being of any social system requires the presence of a ruling element: “Whenever a thing is established out of a number of things and becomes a single common thing, there always appears in it a ruler and ruled …. This [relation] is present in living things, but it derives from all of nature” (Politics 1254a28–32). A human community can only function if it has a ruling element which is in a position of authority, just as an army can only operate if it has a leader.
The rule of reason: Plato states in the Republic (IV.441e) that whenever a system contains a rational element, it is appropriate for it to rule over the nonrational part because the rational element alone knows what is best for the whole. Aristotle elaborates on this principle: different people can be rational in different ways and to different degrees, and therefore different modes of rule are appropriate for different situations. Nevertheless, it is important to use rationality and pragmatism in order to organize social entities. We have experienced different political systems throughout history, societies can outgrow their political systems, and change will follow. Both Plato and Aristotle are skeptical about democracy, because good rule also depends on the rational capacities of the citizens. Both of them favor the rule of law, and good rulers should govern with relative independence, since majority decisions are often not rational choices.