Notice how differently this theory frames the question. Utilitarianism and deontology both ask what makes an action right, treating the agent as whoever happens to be performing it. Aristotle asks what makes a life good, and treats individual actions as expressions of character. That reframing is the whole point, and it explains why the theory offers no decision procedure — because it thinks the search for one was a mistake.
The organising concept is eudaimonia, usually translated as happiness or flourishing, though neither is quite right. It is not a feeling but an activity — living well over a whole life, doing characteristically human things excellently. Aristotle argues that everything else we pursue is pursued for the sake of something further, while eudaimonia is what we pursue for itself, which makes it the final end of action.
Virtues are the stable traits that constitute living well: courage, justice, honesty, generosity, temperance. Crucially, they are not rules but dispositions — settled ways of perceiving, feeling and responding. A courageous person does not consult a principle when danger appears; they see the situation correctly and respond appropriately, and the response includes feeling the right amount of fear. This is why Aristotle says virtues are acquired by practice, the way skills are: we become just by doing just acts, and the doing shapes the disposition.
The golden mean is the most familiar and most misunderstood element. Each virtue lies between an excess and a deficiency — courage between recklessness and cowardice, generosity between prodigality and stinginess. This is not a recommendation of moderation in all things. The mean is relative to the person and the situation, and some acts admit no mean at all. Determining it requires phronesis, practical wisdom: the perceptual judgement to see what a particular situation calls for. This is the master virtue, and it cannot be reduced to rules, which is precisely Aristotle's claim about ethics.
The objectionsWhere the theory strains.
No action guidance. The most common complaint: told to do what a virtuous person would do, someone facing a hard decision is not much helped. Defenders reply that this is honest rather than deficient — moral life genuinely does require judgement, and theories offering algorithms are promising more than ethics can deliver.
Circularity. Right action is defined by the virtuous person, and the virtuous person by having the virtues, which are traits that lead to right action. Whether this is a vicious circle or an interlocking account that has to be grasped whole is disputed.
Cultural variability. Which traits count as virtues has varied considerably across societies. If virtues are culturally contingent, the theory may lack the critical standpoint needed to condemn a whole society's values. Defenders appeal to human nature and the conditions of flourishing as a check.
The situationist challenge. Empirical work in social psychology suggests behaviour is influenced by situational factors far more than by stable character traits, which threatens the theory's foundational assumption. The replication difficulties affecting several of the classic studies have complicated the challenge, and the debate is unresolved — but it is the most interesting empirical pressure any normative theory currently faces.