Full Idea
Justice has no independent existence; it results from mutual contracts, and establishes itself wherever there is a mutual engagement to guard against doing or sustaining mutual injury.
Gist of Idea
Justice has no independent existence, but arises entirely from keeping contracts
Source
Epicurus (fragments/reports [c.289 BCE]), quoted by Diogenes Laertius - Lives of Eminent Philosophers 10.31.35
Book Reference
Diogenes Laertius: 'Diogenes Laertius', ed/tr. Yonge,C.D. [Henry G. Bohn 1853], p.478