QuestionsWhat is happiness?Man is a political animal: one cannot be happy alone
What is happiness?A social matter

Man is a political animal: one cannot be happy alone

Man is a political animal

Aristotle 384 BC · 322 BCObserve, classify, reason: happiness through virtue.
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What it claims

Human happiness is lived with others, in a community: the city exists "for the sake of a good life", and a man alone cannot be fully happy.

Why

Happiness is self-sufficient, and for a being made to live with others, that includes family, friends and fellow citizens.

In short

"Man is a political animal: one cannot be happy alone" is an argument by Aristotle (Nicomachean Ethics I, 7 (1097b); Politics I, 2 (1253a)) on the question "What is happiness?" (answer: a social matter). Its claim: Human happiness is lived with others, in a community: the city exists "for the sake of a good life", and a man alone cannot be fully happy. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 3 objections, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

Nicomachean Ethics I, 7 (1097b); Politics I, 2 (1253a)
Valid with an implicit premise

When Aristotle asks what happiness is, he says it must be "self-sufficient". One might think this means living alone, owing nothing to anyone. He says the opposite. For him human beings are made to live in a community, so a happiness that is self-sufficient is one shared with parents, children, friends and fellow citizens. Someone who needs nobody is not a sage above the rest: he is "a beast or a god".

P1Happiness is the complete good, and the complete good is self-sufficient: nothing else is missing to make life worth choosing.
P2For a being naturally made for the city, being self-sufficient does not mean living alone and cut off: it includes parents, children, wife, friends and fellow citizens.
P3Whoever cannot live in a community, or has no need of it because he is self-sufficient, is no part of the city: he is a beast or a god.
P4 · implicit premiseOrdinary human beings are neither beasts nor gods.
Therefore human happiness is lived with others, in a community: the city exists "for the sake of a good life", and a man alone cannot be fully happy.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P4, nothing rules out that a human being is in fact a "god" who needs nobody: the computer then finds a case where one is self-sufficient without a shared life.
The argument is valid with the hidden premise P4. If one cannot be without a city without being a beast or a god (P3), and we are neither (P4), then we are made for the city. Happiness is self-sufficient (P1), and for such a being self-sufficiency includes others (P2): happiness therefore requires a shared life. The objections target P2 (are we really social by nature?) and the place of others in the sage's happiness.
Analogy. A footballer alone with a ball can practise, but the game, its rules and its feats exist only with others. For Aristotle, human life at its best is like the game: it is not played alone.

Objections

3

Each objection is a conversation: click to see who replies and where the debate stands.

Aristotle himself (Nicomachean Ethics X, 7) 350 BC · attacks premise 2

In the last book of the Ethics, Aristotle says the life of the sage who contemplates the truth is the most self-sufficient: the just man needs people towards whom to act justly, but the philosopher can contemplate "even when by himself", perhaps better with fellow-workers, but without depending on them. Perfect happiness thus seems the least tied to others.

a defender replies
Aristotle (same book, X, 8) defender of the argument · 350 BC
Aristotle adds that the contemplative, "in so far as he is a man and lives with a number of people", chooses to act virtuously and will therefore need such aids to living a human life. The solitary sage is a limiting case, close to the divine; the properly human life remains a life with others.
Where the debate stands (our summary)Our summary: disputed among Aristotle scholars. Some read the Ethics as giving first place to contemplation, others as making happiness a combination of virtuous activities, political ones included. Both readings rest on the text.
Thomas Hobbes 1642 · attacks premise 2

Hobbes holds that the axiom that man is "born fit for society" is false: people come together by accident, for the honour or advantage they find in it, not from a natural love of their fellows. The city is not a fact of nature but a construction by agreement.

no reply
No reply possible: objection raised in 1642, after the author's death (-322).
The debate goes on (our summary) Our summary: Aristotle died 2,000 years before Hobbes and does not answer him. Hobbes himself concedes, in a note, that solitude is an evil for man: children need others to live, adults to live better. The disagreement is about the origin of the city (nature or agreement), less about the need for others.
Where the debate stands (our summary)Our summary: open point. Aristotelians answer that "natural" does not mean "effortless": the city is built, but to realise a capacity nature gave us. Contractualists answer that a capacity to speak and to associate is not enough to make a society natural.
Jean-Jacques Rousseau 1755 · attacks premise 2

In his Discourse on Inequality, Rousseau describes man in the state of nature as wandering in the forests, in no need of his fellows, and self-sufficient. Sociability would not be given by nature: it would come with history, language and the passions.

a defender replies
Aristotle (definition of nature) defender of the argument · 350 BC
For Aristotle, the nature of a being is not its state at the beginning but what it is when fully developed: we say so of a man, a horse or a family. That the isolated man of the beginning has no city therefore proves nothing against a social nature: the city is precisely the fulfilment of his nature.
Where the debate stands (our summary)Our summary: Rousseau and Aristotle answer each other over the meaning of "nature" (starting point or fulfilment). Rousseau says the state of nature is a thought hypothesis, not a fact; whether social life is a fulfilment or a distortion remains open.