The first half of this essay can be read here.
Aristotle ties this quest for happiness into an exploration of those virtues specific to human beings. Virtue, or the fullest expression of a things potential, can be found in every thing, living or otherwise, and many virtues are shared in common between them. The task then, according to Aristotle, is to separate out those virtues exhibited by humanity and humanity alone from those of the animal, vegetable, and mineral kingdom. While some functions (like growth or perception) are shared by all forms of life to one degree or another, others (like reason or piety) are assumed by Aristotle to be uniquely human and therefore reside in the soul.
Scientific data collected since Aristotle’s time have shown that the gap in some reasoning skills between humans and their animal and vegetable cohabitants is not so wide as he assumes as fact. Though the idea that certain behaviors or experiences are unique to the human animal carries some water, it seems more defensible to point to the unique interplay of higher levels of consciousness at work in humanity as the source of that singularity than it does to posit that, if souls exist, then animals don’t have one. The latter view is one nearly unique to Western culture while the former is ubiquitous worldwide.
Setting aside our quibbles with Aristotle’s anthropocentric worldview, it is difficult to argue with his methodology for arriving at happiness as the chief good. In section eight, Aristotle restates his proof in order to move on to a secondary set of observations about its nature. Paraphrased, it can be understood most succinctly as follows.
1. Happiness is the chief good.
2. Goods which are sought for their own sake are better than those sought for the ends they produce as the end is always better than the good itself.
3. Happiness may be sought by means valued for their intrinsic merits or by external means sought for their own end.
4. Therefore, Happiness sought by means valued for their intrinsic merits are distinguishable and indeed superior to those which seek it in the ends of those means.
Once having established happiness as the chief good and, indeed, the fullest expression of human virtue, Aristotle pragmatically asks, “Well, if happiness is so good, then surely we must identify the means to acquire it?” After ticking off a list of possibilities that includes learning, habit and training, he turns to belief, rather than knowledge, to explain the transcendent qualities of happiness, noting that “if there is any gift of the gods to men, it is reasonable that happiness should be god-given, and most surely god-given of all human things insamuch as it is the best” .
This speculation that the gods are in some way responsible for happiness harmonizes with another theme that Aristotle explores in Ethics; namely, that happiness is not immune to external pressures. Events like war and illness may greatly influence an individual’s peace of mind and hamper his or her ability to reach the full potential of their happiness. Moreover, happiness may be earned through diligent effort but it is sometimes also simply received by good fortune; an accident of birth or changing political tides. For Aristotle, the former trumps the latter in value as “to entrust to chance what is greatest and most noble would be a very defective arrangement” .
This idea is broadened later as Aristotle considers the thorny question of when a person might be adequately described as happy. At what point can one truly say that someone is happy as a measure of their life rather than as a snapshot of a single moment within it? If someone can only be said to be truly happy when they have gone beyond external threats to that happiness, then we are led to believe that only the gods and the dead may know it. Furthermore, if the dead may be said to be aware of this state, then musn’t they also be aware of the misfortunes and indignities suffered by their offspring unto infinity thus damaging their hard-earned happiness?
If we are to deny the living true happiness on the basis that we cannot know what may yet happen, happiness seeks nothing but death. If we are to describe the living as happy, then it may not be a sort of happiness dependent on external circumstances else the chief good be achievable only in fits and spurts if at all. Aristotle’s solution is to consider the internal and external factors for happiness as two separate entities. Though he concedes that external events can maim the potential for happiness, “even in these, nobility shines through, when a man bears with resignation many great misfortunes, not through insensibility of pain but through nobility and greatness of soul” .
Returning, at least in spirit, to Socrates’ question (posed in the opening book of Plato’s Republic) of whether a poor good man could enjoy the end of life as much as a wealthy one, Aristotle suggests that each individual must first to decide whether to seek happiness or misery and then hope that fortune turns more often in their favor than not. Happy people, then, beset by ill fortune are still happy but if their fortunes are good, then they are said to be blessed. Those embracing misery, but whom otherwise experience good fortune, will still be miserable but should those fortunes turn against them, then they embody the lowest expression of human potential, wretchedness.
As a final argument to differentiate Happiness from other types of the good, Aristotle observes that as the chief Good, Happiness should elicit something more than praise which is rightly given over to lesser goods. “No one,” he suggests, “praises happiness as he does justice, but rather calls it blessed, as being something divine and better” . Happiness, then, is the chief Good and the standard by which other virtues are measured just as divinity is the standard by which the mortal existence is judged.
Having marched his way across numerous minefields to reach a place of rest, Aristotle closes the first book of Ethics with a concise summation of his inquiry into happiness (designed no doubt as the take-away from the lecture), describing it as “an activity of the soul in accordance with perfect virtue”  . Before closing, he touches briefly on an interesting observation that is prescient in its anticipation of forays into psychology in the 20th century.
There seems to be also another irrational element in the soul—one which in a sense, however, shares in a rational principle…another element naturally opposed to the rational principle, which fights against and resists that principle…That the irrational principle is in some sense persuaded by the rational principle is indicated also by the giving of advice and by all reproof and exhortation. And if this element also must be said to have a rational principle, that which has a rational principle (as well as that which has not) will be two-fold, one subdivision having it in the strict sense and in itself, and the other having a tendency to obey as one does one’s father.
While Aristotle’s language is clumsy in its exploration of largely uncharted waters, this passage does show already a tendency in human thought to compartmentalize the drives that influence behavior and view their interaction as complementary rather than unilateral.