In the community all mutual exchanges are made on the assumption that the parties to them stand to gain.
Gist of Idea
All exchanges in a community are for mutual benefit
Plato (The Republic [c.374 BCE], 369c)
The sole purpose of his society appears to be trading, either of goods or of services. The assumption is that if each individual were self-sufficient there would be no society, which strikes me as unlikely. Aristotle offers a better picture.
Plato: 'The Republic', ed/tr. Lee,Desmond [Penguin 1988], p.118
Idea 19889 People need society because the individual has too many needs [Plato]