Key Arguments

• Justice was implicit from the start in the founding principle: ‘one man should practise one thing only.’
• Repeated formula: justice is ‘doing one's own business, and not being a busybody.’
• Legal practice presupposes justice as ‘having and doing what is a man's own, and belongs to him.’
• Role usurpation (e.g., trader forcing into warrior or legislator) is called ‘the ruin of the State’; the greatest harm to one’s own city is injustice.

Source Quotes

I grow impatient at the length of your exordium. Well then, tell me, I said, whether I am right or not: You remember the original principle which we were always laying down at the foundation of the State, that one man should practise one thing only, the thing to which his nature was best adapted;—now justice is this principle or a part of it. Yes, we often said that one man should do one thing only.

Yes, we often said that one man should do one thing only. Further, we affirmed that justice was doing one's own business, and not being a busybody; we said so again and again, and many others have said the same to us. Yes, we said so.

Yes. Then on this view also justice will be admitted to be the having and doing what is a man's own, and belongs to him? Very true.

Not much. But when the cobbler or any other man whom nature designed to be a trader, having his heart lifted up by wealth or strength or the number of his followers, or any like advantage, attempts to force his way into the class of warriors, or a warrior into that of legislators and guardians, for which he is unfitted, and either to take the implements or the duties of the other; or when one man is trader, legislator, and warrior all in one, then I think you will agree with me in saying that this interchange and this meddling of one with another is the ruin of the State. Most true.

Precisely. And the greatest degree of evil-doing to one's own city would be termed by you injustice? Certainly.

Key Concepts

• one man should practise one thing only, the thing to which his nature was best adapted;
• justice was doing one's own business, and not being a busybody; we said so again and again
• justice will be admitted to be the having and doing what is a man's own, and belongs to him?
• this interchange and this meddling of one with another is the ruin of the State.
• the greatest degree of evil-doing to one's own city would be termed by you injustice?

Context

After ‘hunting’ for justice, Socrates recognizes it as the founding specialization principle; he buttresses the identification by legal criteria and by condemning class usurpation as civic ruin.

Perspectives

Plato

Endorses justice as functional differentiation grounded in nature: each part does its own, preserving the city’s form and enabling other virtues.

Socrates

Insists that meddling is the core civic vice; justice preserves order by keeping traders, auxiliaries, and rulers to their proper work.