In order for a contract to be valid, parties must have capacity: both intellectus ("understanding") and voluntas ("wish", "will").
[4] The orthodox argument is that intention was not an essential condition of Roman contract law, but an integral Byzantium interpolation.
However, David Ibbetson, a British legal academic specializing in Roman law, has argued that the intention of a contracting party was necessary.
D.50.27.48 argues that, in the context of divorce, what was said in anger would not bind unless it was accompanied by action, e.g. a wife saying she will walk out and then doing so.
The Greeks, however, used purely written contracts, which clearly had some influence on Roman law, which did use writing.
More often than not, by the Late Empire under Emperor Leo (which influenced his rescript), the oral stipulation was never in fact made; the documents recorded a non-event.
Diosidi has argued that the stipulatio degenerated further, so far that although theoretically an oral exchange is required, in practice this was not necessary.
He also refers to D.45.1.30,[12] in which a written document purports to be a contract, however this is not incompatible with the arguments of Nicholas.
Nicholas has argued that veluti here means "that is to say" and that the stipulation began as a set list of words that could be used.
Also, it seems strange that a limited list should contain such informal words as dari, meaning simply "to give".
However, Ibbetson has pointed to the requirement of intention and said that this means that an unbounded list was not a problem.
Taking this approach, Riccobono thus argues that C.8.37.10 means that there was no longer any need for question and answer.
This text says that if one party says “Will you give?” and the other says “why not?” he is bound, but if he merely nods, there is no civil or natural obligation.
D.45.1.16 says that if the question is in Latin and the reply is in Greek, the obligation is settled, providing the two correspond.
It states that a moment may naturally intervene but otherwise it should be continuous, and “he” may not begin something else, even if the reply is given on the same day.
That the text expressly rebuts the idea that a reply may be given on the same day after a party has undertaken some other business, suggests that such things were valid at some point in Roman law, although it could be an interpolation.
[19] Stipulation for after death was probably not permissible under classical law because the obligation would reside solely in a third party, the heir.
[20] However, Ulpian, when he states the rule that one party cannot promise for another, makes an exception for heirs, which may mean that it was permissible by that time.
A condition existed when an obligation was framed as arising based on an event that might or might not happen.
[25] An exception to this arose if a party was preventing the condition from occurring, in which case it is treated as having already happened.
[clarification needed] In this case the Romans would have regarded the man as both free and bound at the same time.
However, contrasting the examples given in these two texts suggests that there may have been a fundamental difference between the two types of preposterous conditions.
6.3.52 also speaks on this matter, but it argues that preposterous conditions are both invalid and valid, and appears to have been something like lecture notes, updated with the changes made by Justinian, but without removing the old text.
Furthermore, a suspensive potestative negative condition could be impossible to meet before the death of the person.
Beliefs about swearing held that the gods would prevent someone from telling an untruth under oath.
However, there was little room for flexible interpretation of liability because no questions were asked when the oath was made.
Actio ex stipulatu was a claim for an uncertain thing and would give unliquidated damages e.g. for failure to do something.
This meant that there was leeway in determining the amount of the damages, so it was not a problem that the stipulation was theoretically a stricti iuris.
The exact meaning of duress is unclear from the texts, however, it seems that it needed to be severe and contrary to sound morals,[36] enough affect a man of resolute character,[37] and probably result in a fear of serious evil.
[38] The strict requirements were to be expected; otherwise a party might argue, for example, that they had been forced to enter into a loan contract because they were poor and therefore under economic duress.