The specific rights and duties are referred to as obligations, and this area of law deals with their creation, effects and extinction.
The word originally derives from the Latin "obligare" which comes from the root "lig" which suggests being bound, as one is to God for instance in "re-ligio".
Obligations did not originally form part of Roman Law, which mostly concerned issues of succession, property, and family relationships.
[2] This undesirable situation eventually developed into a system of liability where people were at first encouraged and then essentially forced to accept monetary compensation from the wrongdoer or their family instead of seeking vengeance.
[3] However, liability in this form did not yet include the idea that the debtor "owed" monetary compensation to the creditor, it was merely a means of avoiding punishment.
[5] Justinian first defines an obligation (obligatio)[6] in his Institutes, Book 3, section 13 as "a legal bond, with which we are bound by necessity of performing some act according to the laws of our State.
The main cases are negotiorum gestio (conducting of another person's affairs without their authorization), unjust enrichment, and solutio indebiti.
[11] This Roman classification is quite controversial for today's standards, since many of these cases would be considered as completely different from contracts (most notably unjust enrichment), and would instead be classified as delicts or special sources of obligations.