One may honestly believe that a certain transaction amounts to a contract, when as a matter of fact some essential element of contract is wanting. A benefit conferred in misreliance upon such a supposed contract, under circumstances which make its retention unjust and its restitution not against policy, should be restored.

In the treatment of this subject, it will be expedient in the first place to distinguish the cases of gifts and gratuitous services from those of benefits conferred in reliance upon a supposed contract, and then to consider a variety of cases of the latter sort, which for purposes of convenience may be classified, according to the nature of the defect in the contract, as follows:

A. Acceptance of offer wanting.

B. Assumed fact non-existent.

C. Promise indefinite.

D. Required form wanting.

E. Contractual capacity wanting. F. Authority of agent wanting.