If the state is a compound of different individuals, and the happiness of these will lead to the happiness of the state, it is imperative to understand what the happiness of individuals consists of. The book which extensively deals with the happiness of men and the way this must be achieved is the Nicomachean Ethics. The latter and the politics are in an intimate relationship since: "Aristotle intends the moral inquiry he embarks upon in the Nicomachean Ethics as part of the science of politics" . Ethics is a prelude to political science, without the foundations of Ethics there would not be any good politics.
The essence of all things, men included, is defined, according to the Greek philosopher, in terms of their use and their purpose . The essence of a knife is to cut, and the amount of excellence that a knife can reach is proportional to its capacity of cutting. Human beings are not an exception. Their excellence ( will consist in practicing those virtues which represent their essence. The happiness of man, defined with the peculiar term of eudaimonia (consists in the practice and achievement of excellence. The best and happiest life for men is a life of virtue. Nonetheless not all the virtues possess the same value. He claims that happiness can be reached with the achievement of: external good, good of the body and the good for the soul. Of all these good the soul is certainly superior to all the others since "the goods of the soul are not gained or maintained by external goods" and because the activity of the soul produces happiness by itself. Different men possess different virtues, but of all the qualities the one which best distinguishes man from the other animals and which to the greatest extent should be practised is rationality. The practice of rationality represents for Aristotle the highest good of the soul; it brings to sophia (and this activity brings to the highest happiness. This interpretation of happiness as excellence in virtue has a great stress on practice and self-fulfilment. Happiness is an interior state of mind and our eudaimonia must be achieved independently from other's people view.
Humans nonetheless are not characterised just by their rationality. One of the essential elements for human beings is their sociability, because man is a political animal: "man is by nature an animal intended to live in a polis" . In this case the excellence of 'sociability' is represented by the communitarian life of the polis, which supersedes in order of quality, the life of the household and the life of the village. The polis itself exists by nature and it "prior to the individual" . The man who does not live in a polis must be self-sufficient and in order to be of this kind he must be either be a beast or a god. The polis thus exists both by nature and for the good of individuals. Men associate themselves in the polis not just for mere subsistence, but more essentially, for the well-being of those who participate in its formation. The polis aims to achieve a spiritual improvement of its components and not just satisfaction of needs.
In order to understand what the happiness of the polis is, Aristotle underlines the need of discovering its essence, 'its true nature'. A polis (or a state: the two terms are interchangeable) belongs to the order of compounds. The whole of the polis is formed by the multitude of citizens. Citizenship is the hallmark of the polis. The excellence of the citizens will therefore determine the excellence of the city.
Aristotle defines a citizen as "a man who shares in the administration of justice and in the holding of office" . Nevertheless he understands that this definition does not always apply to the polis since the condition of the citizen described is true only in relation to democracy. Aristotle cannot give a definition of citizenship different from the one proposed because in that case it would not be possible to sustain his theory that essence is determined by purpose. If we defined citizenship depending on birth, it would lose any possibility of excellence because it would be completely disconnected by its function and telos. This definition is therefore the only satisfactory definition which can be given of citizenship.
Aristotle however claims that the nature of citizenship is defined not by citizens themselves but by the constitution of the polis: "if a polis is a form of association of citizens in a polity or constitution, it would seem to follow inevitably that when the constitution suffers a change in kind and becomes a different constitution, also the citizens in that polis will change their identity". Aristotle compares the excellence of each citizen of the polis to that of a sailor performing his own specific duty and capacities for the sake of common safety: "though they differ in the capacities they have they all serve the same aim" . As the performance of the sailor is aimed at the common benefit, so the excellence of the citizen is an excellence relative to the constitution. But with the changing of the constitution also citizenship changes. At this point the duality between the excellences of the individual becomes evident. It is sufficient to underline that the excellence of the good citizen aims at the achievement of the good not within himself but to one outside, to show that good man and good citizens follow two different paths. Aristotle himself underlines this dichotomised nature of the individual. If excellence of the citizen changes according with the changing of the constitution, the excellence of the good man remains the same and there is no possibility of concealing the two: "it is thus clear that it is possible to be a good citizen without possessing the excellence which is the quality of the good man" . Citizenship and morality are not inextricably linked.
Moreover with the changing of the constitution, the definition of citizenship offered by Aristotle becomes unattainable. If citizens are described as office-holders, then in aristocracy and kingship the number of those who could be considered as citizens as meant by Aristotle are reduced in number. In the monarchical constitutions there would not be citizens anymore, but just subjects and the state would consist of just one element. The monarch would be the only office holder.
Nevertheless, Aristotle claims, a polis can still reach happiness if it works following the principle of distributive justice, which implies the recognition of the contribution that each citizen makes to promotion of a good quality of life; the operative aim of the polis is always the promotion of the good quality of life and "those who contribute most to the realisation of that aim should in justice have more rights" . The adoption of the principle of distributive justice distinguishes right constitutions (monarchy, aristocracy and polity), from their negative reflection (tyranny, oligarchy and democracy). The distinct feature is that the tyrant, the oligarchs and the democrats work to increase their own good, while the monarch, the aristocrats and the polites aim to achieve the good for the community. But even in their perspective doubts arise. If distributive justice implies the recognition of merit also in terms of rights, then the monarch should involve meritorious people to participate in the political life holding offices. This change would consequently change the constitution of the government making monarchy more a sort of aristocracy for example. In this sense what is unclear is the relationship between constitution and citizenship. At the beginning it seems that constitution would determine the form of citizenship. With the proceeding of the argument the opposite seems to become true with citizenship defining constitution.
Moreover another problem becomes evident with the assumption of monarchy or aristocracy as forms of government. If under monarchies do not possess any share in the holding of the political office, and therefore cannot exercise their capacity of choice, what would distinguish them from slaves? If the possibility of exercising their political excellence is limited by the constitution how then is it possible for monarchy to be a good constitution. If the purpose of the individual under monarchy is to be a subject, there is no difference between a subject and a slave.
The discrepancy between citizenship and morality is also proven by the example of the man too virtuous to remain within the political community. This is evidently the most notable case of the fact that being a good citizen can possibly be even the contrary of being a good man, since the excellence of a man could work against the institutions and its laws since he would be superior to the laws. Such a man would too good to follow the constitution and would therefore pose a threat to it. This sustains the view that men can be good even when the constitution is ruinous. But then this proves that the happiness of the individual is not linked with the happiness of the state. The excellent man will remain excellent even outside the polis.
Throughout the text we witness a tension between the idea of citizenship and morality, which is also the tension between practice and speculation, the life of the philosopher and the life of the statesman. Aristotle tries to conciliate speculation by claiming that the activity of the mind of the mind is a self-contained activity: "the self-contained individual - like the self contained state - may be busily active: the activity of God and the universe is that of a self-contained life". But Aristotle knows that human beings are not only reason and that they cannot reach self-sufficiency by their only endeavour. Autarky is not completely possible, neither for the individual nor for the state. Man is made, as Aristotle himself claims, by instincts, necessities and rationality and it therefore seems that the ideal state cannot be reached in this world.
The relationship between the happiness of the state and the happiness of the individual is not always the same and in some cases it can even diverge (e.g. in the case of the excellent man in an imperfect constitution). From a comparative analysis of the book constituting the Politics differences appear on what should be considered as the best form of government (e.g. the mese politeia or the aristocracy), and in the relationship between the excellence of the citizen and the excellence of man, even in the definition of citizenship and also in the concept of autarky. Some of these discrepancies can be justified by the fact that the Politics is a composite work, it consists of a collection of notes more than an organic composition. Werner Jaeger moreover has suggested that the Aristotle composed the Politics in two different periods and that these are particularly notable in relation to book III and VII, produced in an early phase, and of books III and VI, composed in a later period. But the main reason for these discrepancies is that "Politics is not an exact science" because the subject matter (men) is not of the same kind as the other sciences. Men is both a rational and irrational being, he acts, by instinct, by necessity and by reason and it is therefore impossible to construct a system which could satisfy the requisites of such a complex subject. The science of politics requires flexibility.
The latter is also needed to understand the relationship between the happiness of the state and the happiness of the individual. Perfection and certainty cannot be reached because of our human condition, but the attempt to achieve them is already cause of happiness both for the state and for the individual.