The doctrine of course has its roots in the early common law. A study of its history would reveal that the personal actions of covenant and debt are the 2 aspects which have helped the evolution of the doctrine. The action of covenant was the action which was brought upon instruments which are enforceable by the virtue of their form. After a period of hesitation , it was settled in Edward I reign that , it was only the sealed writing which could be received as originally bound , not because the sealed writing evidenced an agreement , but because it was conclusive proof that the defendant had come under a liability to the plaintiff.
Originally the action of debt was hardly distinguishable from another action of detinue. In the course of time debt tended to become more contractual in nature , while detinue tended to become somewhat more proprietary or delictual . In fact , action of debt , like the action of covenant , was as often as not brought upon contracts ; just as contracts under seal were supposed to be brought into line with a general theory of contract , by the fiction that the seal imports consideration , so all causes of action upon which the action of debt could be brought were by various fiction , supposed to be of contractual origin. But , despite this neither debt nor detinue ever became completely contractual or completely proprietary or delictual.
In the action of debt , the defendant was conceived of as having in his possession , something belonging to the plaintiff which he might not rightfully