QuestionsWhat is a just society?Citizen of the world
What is a just society?One humanity

Citizen of the world

Marcus Aurelius 121 · 180What is not up to you should not trouble you.
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What it claims

The world is like a city, and every human being is my fellow citizen: as a man, my country is the world.

Why

We all share reason, hence a common law, hence one city: the world.

The same idea through history
Diogenes of Sinope350 BCThe first to call himself a "citizen of the world" (kosmopolitês), according to Diogenes Laertius: asked where he came from, he answered that he was a citizen of the world. In Marcus, the word rests on the reason shared by all rational beings.
In short

"Citizen of the world" is an argument by Marcus Aurelius (Meditations IV, 4; VI, 44; II, 1) on the question "What is a just society?" (answer: one humanity). Its claim: The world is like a city, and every human being is my fellow citizen: as a man, my country is the world. According to AskPhilosophy's logic check (Z3 solver), the conclusion does follow from its 4 premises. AskPhilosophy presents 3 objections, 1 of them with a documented reply, and the original text behind each premise, checked word for word.

Meditations IV, 4; VI, 44; II, 1
Valid

The most powerful man in the Roman Empire writes that his true homeland is not Rome but the world. His reasoning starts from a simple idea: all humans share reason. From there, step by step, he concludes that we are all fellow citizens of one city.

P1All human beings share intelligence, the reason that makes us rational beings.
P2If reason is common, the reason that commands what to do or not to do is common too: so we have a common law.
P3Those who share a common law are fellow citizens, members of one political community.
P4If all humans are fellow citizens, their city can only be the world: it is the only community of which the whole human race is a member.
Therefore the world is like a city, and every human being is my fellow citizen: as a man, my country is the world.

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.
The argument is a chain of "if... then": it is valid as Marcus writes it, with no hidden premise. So the whole debate is about the premises. P2 assumes that one and the same reason gives one and the same law for all (is that true, when peoples have different laws?). P3 assumes that a common law is enough to make a city, even without a government, borders or common power. Note: Marcus does not abolish the local homeland. He writes: "as Antoninus, my city is Rome; as a man, it is the world".
Analogy. Players from all over the world who have never met follow the same rules of chess: everywhere, they form one community of players. For Marcus, reason is a common rule of this kind, but for the whole of life.

Objections

3

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

Thomas Hobbes 1651 · attacks premise 3

Where there is no common power, there is no law; where no law, no justice. A "world city" without a government or force to enforce its rules is not a city: between peoples, the state of nature prevails.

no reply
No reply possible: objection raised in 1651, after the author's death (180).
Rousseau (Emile, book I) 1762 · attacks the conclusion

Beware of cosmopolitans who seek far away in their books duties they neglect around them: such a philosopher loves the Tartars so as to be excused from loving his neighbours.

Marc Aurèle replies
summary: their text is not yet in our corpus
Marc Aurèle What Marcus writes about his two homelands (Rousseau came sixteen centuries later)
As Antoninus, my city and country is Rome; as a man, it is the world. Only what is useful to these cities is good for me.
The debate goes on (our summary) Rousseau would answer that double membership settles nothing: when the interests of Rome and of the Marcomanni clash, the emperor goes to war for Rome. The world homeland remains an idea, the local homeland a reality.
Aristotle 330 BC · attacks premise 4

Man is by nature a political animal, but the city has a natural size: citizens must be able to know one another and deliberate together. The whole human race cannot form a city, only a crowd.

no reply
summary: their text is not yet in our corpus
We have not yet found a direct reply by Marc Aurèle in the texts.