Book 10 closes the Ethics by returning to pleasure and asking what life most fully realizes happiness. Aristotle begins where educators already live: young people are steered by pleasure and pain, and learning to enjoy what one ought and hate what one ought shapes character across a whole life. Some thinkers call pleasure the good, others treat it as thoroughly bad and try to push people away from it even if that means distorting the truth. Aristotle rejects both shortcuts. Arguments about feelings and actions are less persuasive than lived facts, and a moralist seen secretly chasing pleasure discredits his own teaching because most people cannot draw fine distinctions. True arguments harmonize with experience and move those who grasp them to live accordingly.
He then reviews rival theories. Eudoxus argued that all things aim at pleasure and that what all pursue must be the chief good; Plato replied that if wisdom makes the pleasant life more choiceworthy, pleasure cannot itself be the good. Aristotle accepts that pleasure is a good but not the only good, and he denies that pleasure is mere motion or replenishment of a lack. Pleasure completes activity the way bloom perfects youth: it supervenes on a power acting well on its proper object. That is why pleasures differ in kind with activities, why proper pleasure intensifies geometry or music while alien pleasure destroys argument when flute playing distracts the student, and why the good man's pleasures are the measure of what is truly pleasant for a human being. Disgraceful pleasures are not pleasures except to a ruined taste, just as bitter food is not sweet to a sick palate. Even memory and hope can please without prior pain, which undermines theories that treat every pleasure as mere replenishment. The friend differs from the flatterer because one consorts with us for the good and the other for pleasure alone, and no one would choose a child's mind for a lifetime of childish amusements.
Having treated virtue, friendship, and pleasure, Aristotle sums up happiness. It cannot be a disposition you could possess while asleep or in misery; it must be activity, and the best activity will belong to the best part of us. Leisure is necessary because politics and war exist for the sake of peace and the activities of peace, not the reverse. Contemplation is most continuous, most loved for itself, and most self sufficient. The life of the gods, if they live at all, cannot be contracts, deposits, or temperance about bad appetites; what remains for blessed beings is contemplative activity, and the human life most akin to that is happiest. Moral and political virtue still matter in a secondary degree because justice, courage, and practical wisdom belong to our composite nature and require external goods, friends, and opportunities to act. The philosopher needs less equipment for his highest work than the statesman needs for noble deeds, yet even contemplators remain human and choose virtuous action among others.
Aristotle insists that perfect happiness is contemplative activity, not because ordinary life is worthless, but because reason is what is most authoritative in us. We should, so far as we can, live by the best thing in us even though it is small in bulk compared with the body. External prosperity is still required for health, food, and leisure, though moderate means suffice for noble action and the happy person should not be confused with the merely wealthy or powerful. Solon and Anaxagoras sketch a life that looks strange to crowds who judge by externals alone; the decisive test is whether theory fits the facts of life. Those who exercise reason seem best minded and dearest to the gods, if the gods care for what is best and most akin to them.
The book ends by admitting the limit of theory. Knowing virtue is not enough; we must have and use it. Arguments encourage the generous minded but rarely remould people formed by long habit to pursue passion and avoid pain without ever tasting what is noble. Character must already love the fine and hate the base; right nurture from youth, continued habit in adulthood, and laws with compulsive force are therefore necessary. Paternal commands lack the power of law, yet households and cities both shape souls through custom. Where public education fails, each person should help children and friends toward virtue, and the one who would make others good should study legislation, since good laws are how communities become capable of goodness. Experience matters in politics as in medicine, but the sophists who claim to teach statesmanship often mistake rhetoric for wisdom and think laws can be collected without judgment. Private education can suit individuals as private medicine can, yet the legislator who knows the universal still guides the whole. Aristotle thus closes the Ethics by opening the Politics: ethics describes the end, but law and constitution are still required if human beings are to live it.
