Obligations were classified by the jurists into two main cate gories, according as they arose from delict (tort) or contract : the remaining obligations the Byzantines placed under the head ings of quasi-contract and quasi-delict.
I. Delict.—The XII. Tables already show the law in a state of transition from the system of private vengeance to that in which the state insists on the acceptance of compensation instead of vengeance by the person wronged and fixes its amount. Thus in the case of assault (iniuria) if one man broke another's limb, talion was still permitted, i.e., the person wronged could inflict the same injury as he had received, but in other cases there were fixed money penalties, e.g., 25 asses for a blow. Theft involved a penalty of twice the value of the thing stolen, unless the thief was caught in the act (furtum manifestum) in which case he was flogged and "adjudged" to the person wronged.
In classical times, praetorian reforms had substituted a four fold penalty in the case of furtum manifestum and penalties for iniuria (which now included defamation and insulting behaviour) were assessed in each case by the court. The law of damage to property was regulated by a statute (lex Aquilia) dating from the republic, but later than the XII. Tables, much extended by inter pretation and by the praetor, and praetorian actions lay for a number of new delicts of varying importance.
II. Contract.—At the time of the XII. Tables a law of con tract can hardly be said to have existed, though we know of an institution called nexum of which hardly anything can be said with certainty except that it was a kind of loan so oppressive in character that it might result in the debtor's complete subjec tion to the creditor. It was obsolete long before classical times. The contracts of classical law were divided into four classes, literal, verbal, real and consensual. The literal contract was a type of fictitious loan formed by an entry in the creditor's account book; it was comparatively unimportant, and obsolete in Jus tinian's day. The verbal contract or stipulatio was of great impor tance, for it provided a form in which any agreement (provided it was lawful and possible) might be made binding by the simple method of reducing it to question and answer, e.g., "do you promise to pay me ten thousand sesterces?"—"I promise." Originally it was absolutely necessary that the words should be spoken, but it may be said (technicalities apart) that by Justinian's day a writ ten memorandum of such a contract would be binding, even though in fact there had been no speaking at all. If an agree
ment was not clothed in the form of a stipulation, it must, to be valid, fall, according to its content, under one of the types of real, or consensual contracts. A real contract is one which needs for its conclusion (in addition to the consent of the parties) that some thing should be transferred from one party to the other and that the obligation arising should be for the return of the thing transferred. The real contracts are mutuum (loan, e.g., of money), commodatium (loan, e.g., of a horse), deposit and pledge. Con sensual contracts need no element for their formation except agreement—whether expressed in words or otherwise—between the parties, and though there were only four such known to the law, these were the most important in ordinary life—emptio venditio (sale), locatio conductio (hire of things or services and also giving out jobs to be done), societas (partnership) and man datum (agency). In Justinian's day it was further a principle that in any case of reciprocal agreement, e.g., an agreement for ex change (which was not sale), if one party had performed, he could bring an action to enforce performance by the other ("innominate contract").