5. It is customary to insert a particular place in a stipulatio, as, for instance, “Do you engage to give me at Carthage?” and this stipulatio, although it appears to be made simply, yet necessarily implies a delay sufficient to enable the person who promises to pay the money at Carthage. And therefore, if anyone at Rome stipulates thus “Do you engage to give to me this day at Carthage?” the stipulatio is useless, because the thing promised is impossible.
6. Conditions, which relate to time present or past, either instantly make the obligatio void, or do not suspend it in any way; as, for instance, “If Titius has been consul, or if Maevius is alive, do you engage to give me?” If the thing mentioned is not really the case, the stipulatio is void; if it is the case, the stipulatio is immediately valid. Things certain, if regarded in themselves, although uncertain as far as our knowledge is concerned, do not delay the formation of the obligatio.
7. Not only things, but acts, may be the subject of a stipulatio: as when we stipulate that something shall, or shall not, be done. And, in these stipulationes, it will be best to subjoin a penalty, lest the amount included in the stipulatio should be uncertain, and the plaintiff should therefore be obliged to prove how great his interest is. Therefore, if any one stipulates that something shall be done, a penalty ought to be added as thus: “If the thing is not done, do you engage to give ten aurei by way of penalty?”
But, if by one single question a stipulatio is made that some things shall be done, and that other things shall not be done, there ought to be added some such clause as this: “If anything is done contrary to what is agreed on, or anything agreed on is not done, then do you engage to give ten aurei by way of penalty?”
XVI. Obligatio By Consent.
Obligationes are formed by the mere consent of the parties in the contracts of sale, of letting to hire, of partnership, and of mandatum. An obligatio is, in these cases, said to be made by the mere consent of the parties, because there is no necessity for any writing, nor even for the presence of the parties: nor is it requisite that anything should be given to make the contract binding, but the mere consent of those between whom the transaction is carried on suffices.
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