De rerum permutatione
(Concerning the Exchange of Property.)
1Paulus, On the Edict, Book XXXII. Just as it is one thing to sell, and another to buy, and as a difference exists between purchaser and vendor, so the price is one thing, and the property another. In an exchange, however, it cannot be ascertained which is the purchaser and which the vendor. Exchanges differ greatly, for a purchaser is liable to an action on sale, unless he pays the purchase-money to the vendor; and it is sufficient for the vendor to bind himself in case of eviction, to deliver possession and be free from fraud, and therefore, if the property sold is not lost by a better title, he owes nothing. In an exchange, however, if the property of each party is regarded as the price of that of the other, the title to each article must pass, but if it is considered as merchandise, neither is required to transfer the ownership. But, while in a sale there must be both property and a price, it cannot be ascertained in an exchange which is the property, and which is the price, nor does reason permit that the same thing shall be at once the property sold and the price of what is purchased. 1Wherefore, if one of the articles which I have received or given is afterwards taken away through a better title, it is held that an action in factum should be granted. 2Moreover, purchase and sale is contracted by the mere will of the parties consenting to the same; an exchange, however, gives rise to an obligation by the delivery of the property. Otherwise, if the property was not delivered, we hold that an obligation could be contracted by mere consent, which is only applicable to agreements of this kind which have their own specific designations, as purchase, sale, lease, and mandate. 3Therefore Pedius says that where a party gives property which belongs to another an exchange is not contracted. 4Hence, where delivery is made by one party, and the other refuses to deliver his property, we cannot institute proceedings for the reason that it is to our interest to have received the article concerning which the agreement was made; but there will be ground for a personal suit for recovery to compel the property to be restored to us, just as if the transaction had not taken place.
2Ad Dig. 19,4,2Windscheid: Lehrbuch des Pandektenrechts, 7. Aufl. 1891, Bd. II, § 392, Note 2.The Same, On Plautius, Book V. Aristo says that an exchange resembles a sale in a case where a guarantee must be given that a slave is sound, and free from liability to arrest for theft or damage committed, and that he is not a fugitive who must be surrendered on this account.