Section 1. On Purchase and Sale in General

587. Notion. Purchase-sale is a contract by which two persons agree between themselves concerning merchandise to be handed over for a price. Therefore three things pertain to the essence of this contract: a. mutual consent of buyer and seller; b. some thing, either movable or immovable, as merchandise; c. money as price.

a. This contract in itself is indeed one; but because it necessarily involves two acts, buying and selling, it is usually signified by the joined double name purchase-sale.

b. Sale is a consensual contract, which is perfected by consent alone; therefore by natural law neither the handing over of the thing and price nor any solemnity, for example writing, is required for the essence of this contract. Yet positive laws generally establish that by consent itself only a right to the thing is acquired, namely, on the part of the buyer, the right of accepting the merchandise, and on the part of the seller, the right of accepting the price; but ownership or the real right in the merchandise and in the price is acquired only by the handing over of the merchandise and price.¹ These dispositions of law must also be observed in conscience, unless the contracting parties themselves knowingly and voluntarily establish something between themselves contrary to the dispositions of civil law, which they can licitly do, provided they preserve the norms of natural justice.

c. For the essence of this contract it is required that it be made concerning merchandise on the one side and money on the other side, or concerning a price to be handed over for merchandise and merchandise for a price: for if on each side it is made concerning merchandise, there is not sale but exchange; and if on each side it is made concerning money, there is exchange of money.

¹ Thus also C.A. Section 1053 and C.G. Section 433, with which Roman law agrees, but not English nor Belgian law.

588. Division. 1. Purchase-sale is divided into natural and artificial. It is called natural or economic if those things are bought which are necessary for sustenance, and superfluous things are sold; and it is called artificial if things are bought with the intention of selling them with gain. Artificial purchase-sale is called trade.

2. Artificial purchase-sale is twofold: lucrative, when a thing is bought so that, without change of itself, it may be sold at a higher price; and simply artificial, when a thing is bought so that it may be changed naturally or by industry and, once changed, be sold at a higher price. By the former sale trade is exercised in the stricter sense; by the latter, trade in the broader sense.