In the Nicomachean Ethics, Aristotle presents a systematic investigation of the human good, ultimately identifying it with happiness (eudaemonia) understood as virtuous activity of the soul. This paper will examine Aristotle’s characterization of the human good and traces his argument as he derives happiness as the highest good. Finally, it will deconstruct the argument and show how Aristotle’s happiness is impossible to achieve.

Aristotle begins his investigation of the human good with an observation on the nature of rational action: “Every art and every inquiry, and similarly every action and choice, is thought to aim at some good” (1094a1-2). Different activities aim at different goods – medicine at health, shipbuilding at vessels, military strategy at victory. However, some ends are subordinate to others (instrumental ends), meaning some ends are in service of a greater good and don’t fulfil a complete good in and of itself. Ends can thus be understood as being hierarchical, however this hierarchy of goods must be finite as if every choice were for something else, our desires would be “empty and vain” (1094a21). Therefore, there must be a final good in which all of our ends point to.

Aristotle argues, this final good must meet two key criteria. As he states, “we call final without qualification that which is always desirable in itself and never for the sake of something else” (1097a30-34). This establishes the first criterion of completeness - the good must be chosen always for itself and never for anything else. The second criterion is self-sufficiency, which Aristotle defines as “that which when isolated makes life desirable and lacking in nothing” (1097b14-15). Additionally, Aristotle contends that this good must be intimately connected to the human function or ergon. The function argument states, just as a knife’s function is to slice, human beings must have a distinctive human function unique to our faculties as rational creatures. It cannot be mere life, as this we share with plants, nor mere perception, which we share with animals. Therefore, the human function must involve that which makes man unique, rational activity. Furthermore, just as a good knife is a knife that cuts excellently, for a human to be achieving the ultimate good, they must in kind perform their function excellently, as the good of anything lies in performing its distinctive function well. Aristotle thus argues that “human good turns out to be the activity of the soul in accordance with virtue, and if there are more than one virtue, in accordance with the best and most complete” (1098a16-18). To understand this statement, we need to understand Aristotle’s perspective on the soul and virtue.

Aristotle understands the soul to contain two parts, the rational and non-rational part, each divided into two subcategories. The rational soul’s consists of the scientific part, which engages with unchangeable truths (“the invariable”) such as mathematical principles and natural laws and the calculative part which engages with practical matters that can be changed through human action, including skills, crafts, and character development (1139a11-13). The non rational includes the biological, concerned with functions like nutrition and growth, and psychological, concerned with matters such as emotions and desires. As he explains, “we praise the reason of the continent and incontinent person, and the part of their soul that has reason, since it urges them in the right way and toward what is best; but there is clearly also another element in them which is naturally opposed to reason” (1102b14-18). Crucially, while the non-rational part may resist the rational, it can be trained to align with it (and indeed aid it), distinguishing humans from both plants, which have only nutritive capacities, and animals, which have perception but cannot develop rational control over their desires.

Aristotle defines virtue as “a state of character concerned with choice, lying in a mean, i.e., the mean relative to us, this being determined by reason, and by that reason by which the man of practical wisdom would determine it” (1106b36-1107a2). This manifests in two distinct but interrelated forms: intellectual and moral virtues. As Aristotle explains, “Virtue too is distinguished into kinds in accordance with this difference; for we say that some of the virtues are intellectual and others moral, philosophical wisdom and understanding and practical wisdom being intellectual, liberality and temperance are moral” (1103a3-7). These virtues are not merely abstract qualities but enable the rational soul to function excellently. Intellectual virtues are “both produced and increased by instruction” while moral virtues come about “as a result of habit” (1103a14-17). Together, if cultivated and habitualised, they form a complete system of excellence that enables the rational soul to function optimally in both theoretical contemplation and practical action. As Aristotle emphasizes, “the function of man is an activity of the soul which follows or implies reason” (1098a7-8), and virtue is precisely what enables this function to be performed well.

Having established the structure of the soul and the nature of virtue, we can see how these elements complete Aristotle’s argument. The excellence of rational activity, expressed through both intellectual and moral virtue, meets his criteria of completeness and self-sufficiency while fulfilling our distinctive human function. This allows Aristotle to identify happiness with virtuous activity of the soul.

A fundamental objection to Aristotelian happiness lies in its impossible demands on human nature. The soul requires completion across multiple domains: the scientific part demands mastery of eternal truths, the calculative part requires perfect practical judgment, the biological aspect needs optimal physical functioning, and the psychological aspect demands rational control over all emotions and desires. Yet each domain faces insurmountable limitations. Our knowledge constantly reveals new unknowns, our bodies inherently degrade through biological entropy, and our emotions resist rational control - as Hume argues and modern psychological research by Haidt confirms, reason serves rather than commands our passions. Aristotle may counter saying this is a misunderstanding of his conception of virtue, claiming it requires not absolute perfection but excellence relative to human nature - not omniscience but wisdom, not fearlessness but appropriate fear (the virtue of the mean). However, this defense creates an insurmountable problem of threshold - what level of excellence suffices? Any standard becomes arbitrary. More fundamentally, accepting limited excellence contradicts Aristotle’s own requirement that happiness demands activity in accordance with the best and most complete virtue. We face an irreconcilable dilemma: either maintain complete virtue, making happiness impossible, or accept partial virtue, undermining Aristotle’s entire framework of happiness.

In examining the Nicomachean Ethics, we see Aristotle construct an intricate argument linking human happiness to virtuous activity of the soul. His reasoning moves from the observation that all actions aim at some good, through the requirements of completeness and self-sufficiency, to the identification of happiness with excellent rational activity. The argument’s strength lies in how it connects human nature, through our distinctive rational function, to an objective conception of the good life. However, this very systematicity reveals its central weakness - the unbridgeable gap between Aristotle’s demands for complete virtue and the inherent limitations of human nature. While his analysis of virtue and excellence provides invaluable insights into human flourishing, his conception of happiness ultimately sets an impossible standard. However, the enduring value of Aristotle’s ethical framework lies not in its final conclusions, but for providing a blueprint for human fulfilment, illustrating the facets of life which we should strive to perfect in our own quest for happiness.