954. Contracts produce obligations, and sometimes have the effect of discharging or modifying other contracts.
They have also the effect in some cases of transferring the right of property.
They can be set aside only by the mutual consent of the parties, or for causes established by law.
955. Contracts have effect only between the contracting parties; they cannot affect third persons, except in the cases mentioned in the articles of the Fifth Section of this Chapter.
956. The obligation of a contract extends not only to what is expressed in it, but also to all the consequences which, by equity, usage or law, are incident to the contract, according to its nature.
957. A contract for the alienation of a thing certain and determinate makes the purchaser owner of the thing by the mere consent of the parties. Movables must be delivered in order to affect third parties, and in the case of immovables there must be a deed of sale, or memorandum in writing, stating the conditions of the sale.
958. If the thing to be delivered be uncertain or indeterminate, the purchaser does not become the owner until it is made certain and determinate, and he or she has been notified to that effect.
959. If a party contract successively with 2 persons separately to deliver to each a thing which is purely movable property, that one is owner who has been put in actual possession, although his or her title be posterior in date; provided, however, that his or her possession be in good faith.
960. Such of the rules of this section as are applicable to immovable property are subject to the provisions respecting registration as regards their effect upon third parties.