Your overview of Aristotle’s view of the good life and it’s relationship to the life of the city is, in the broad sense, solid. However, if you don’t mind, I’d like to submit to you a few alternate considerations on your assumptions.
The idea that human beings are political creatures is derived from his famous line that ”ό αντηρώπος φυσις πολιτικών ζωον.” This can roughly be translated as “Human beings, in their nature, are political creatures (or, perhaps even more literally, are animals of the city. The first Greek word is “anthropos” which means mankind and is not “andros” which means male). This is the defining characteristics of a human being in the same way that a fish is defined by swimming; it is the defining characteristic of the species. What is left to consider is what is the excellent form of the activity of human beings — in that, an eye has a perfect function in perfect sight, a wheel has a perfect function in perfect rolling, etc. If a human being is defined by political life, what is the most excellent form of that life and how does it manifest itself in reality?
With this as the starting foundation, Aristotle’s conception of the good life is aimed at understanding what is the best for a human being, as opposed to all other creatures — what are the defining attributes of human beings which separate them from other animals. Herein lies the discussion of the virtues from the Nichomachean Ethics. The virtues are those things which characterize man’s ability to behave differently than other animals, and, therefore, represent a facet of that which defines our excellence. You rightly point out that he also considers the philosophical life as part of it since human life is also derived from our cognitive capacities. Both in Book 1 and 10 of the Nichomachean Ethics, however, he wrestles with the idea that human life is best defined to the pursuit of knowledge and wisdom; that to live this way without regard to the life of the city is above the life of human beings, this is now the life of God. Therefore, human life must be defined as this intersection between the desire to gain wisdom and the need to live out our natural calling in political life, and, thus the need to study “phronesis” or practical wisdom, namely politics and ethics. It’s all derived from the same source — the natural condition of man as a political creature since he has the capacity to speak and to think which gives him the aptitude to be discerning (to evaluate good from bad, justice from injustice).
I believe to this point we agree in our interpretations, at least broadly. Where I would like to encourage you to reconsider is the role of slavery and the idea of sharing in ruling and being ruled. The later point is how Aristotle defines a citizen — one that shares in ruling and being ruled. Citizenship, then, is characterized by power asymmetry — in the need to understand the rule of law as applying to you both when you are actively exercising political power and when you are not. Power asymmetry, however, is not merely the foundation of citizenship but of political life itself. Politics is defined by human beings discerning between justice and injustice — recognizing that both will exist in all political societies. Given that justice, whether speaking of distributive, proportional, or absolute, is predicated on balancing the allocation of honor or wealth or other metric of human activity, presumes an allocator and an allocated; this holds true in a tyranny or a kingship, a polity or a democracy. Power asymmetry is the definitive condition of political life, and, as such, citizenship is therefore based on this same principle. The issue becomes who is included in ruling and who is merely ruled — the variation of which is the foundation of his exploration of regime type.
Given that power asymmetry is definitive of political life, what does this mean for slavery. Aristotle’s defintion of a natural slave, which you allude to, indicates that a slave is one who does not share in the rational faculties — those same rational faculties which are definitive of being a human being. This seems to indicate that Aristotle is arguing that slavery, in the owning of another human being as a labor force, is not a natural condition but one which exists by convention. This convention, while serving a vital role in the life of the city by allowing free time (σχόλη — schole) for philosophy and politics, should not be confused with seeing slaves as being less than human. To the contrary, natural slaves must love their masters because their masters rule on the behalf of the slave. Someone, then, who is natural slave is one who is fully dependent on another, a caregiver in our modern vernacular, and not one who is going to be of much use beyond the most menial of tasks.
Slaves are not fit for citizenship because they lack the necessary virtuous education in order to share in ruling and being ruled — they are only educated to the later and, therefore, to enfranchise them without rehabituating them to the necessary virtues will undermine the virtue of self-government and will aid in confusing the life of virtue with the life of pleasure. One requires a virtuous education in order to move beyond the base desires of human beings; those who lack such an education may no longer be the slave to another but are a slave unto themselves.
The good life, then, is one which is lived within the political community, engaged in the political life, in sharing in ruling and being ruled, and living in accordance with virtue. Virtue here being “arete” which means excellence, returning us back to the starting notion of the inquiry — what is the thing which separates human being from the other animals which can be done excellently by the species? Living virtuous lives in the city, man’s natural condition. Therefore, the virtues are as defining of human beings as swimming is to fish, seeing is to eyes, and rolling is to wheels. The good life, then, is one predicated on living in accordance with excellence in activity (Aristotle’s defintion of happiness) and thus can be summarized as follows: the good life is the happy life.
Thank you for your initial post and for wrestling with these ideas. Far too few engage with perhaps the most important question we can ever ask — what is the best way to live?