"Then the workers of our city must not only make enough for home consumption; they must also produce goods of the number and kind required by other people?"
"Yes, they must"
"Then our city will need more farmers, and more of all the other craftsmen?"
"Yes"
"And among the rest it will need more agents who are to import and export the different kinds of goods. These are merchant, are they not?""
"Yes"
"We shall need merchants, then?"
"Certainly"
"And if the commerce is over sea, we shall need a host of others who are expert in sea-trading"
"Yes, there will be many of them"
"Again, in the city itself how will men exchange the produce of their labours with one another? For this was the original reason of our establishing the principle of community and founding a city"
"Clearly, by selling and buying"
"This will give us a market-place, and money as a token for the sake of exchange"
"Certainly"
"Then if the farmer or any other craftsman brings his produce into the market-place, and meets there none who wish to exchange their goods with him, is he to sit idle in the market-place when he might be working?"
"Certainly not. There are men who have taken note of this,and devote themselves to this service. In well-governed cities they are usually those who are weakest in body, and incapable of any other work. They have to stay there in the market-place and exchange money for goods with those who want to sell, and goods for money with those who want to buy"