2. This contract differs from a sale in this, that barter is always of goods for goods, whereas a sale is an exchange of goods for money. In the former there never is a price fixed, in the latter a price is indispensable. All the differences which may be pointed out between these two contracts, are comprised in this; it is its necessary consequence. When the contract is an exchange of goods on one side, and on the other side the consideration is partly goods and partly money, the contract is not a barter, but a sale. See Price; Sale.
The same thing holds true of all other possessions; for barter, in general, had its original beginning in nature, some men having a surplus, others too little of what was necessary for them: hence it is evident, that the selling provisions for money is not according to the natural use of things; for they were obliged to use barter for those things which they wanted; but it is plain that barter could have no place in the first, that is to say, in family society; but must have begun when the number of those who composed the community was enlarged: for the first of these had all things in common; but when they came to be separated they were obliged to exchange with each other many different things which both parties wanted.