The general nature of quasi contractual obligations is revealed by the foregoing sketch of their origin. They may be defined as legal obligations arising, without reference to the assent of the obligor, from the receipt of a benefit the retention of which is unjust, and requiring the obligor to make restitution.1 Their chief distinguishing characteristics are as follows:

1 For an excellent discussion of the nature of quasi contracts, see Professor Corbin's article on "Quasi-Contractual Obligations," 21

1. They are paramount or irrecusable, as distinguished from consensual or recusable, obligations.1 That is, they are imposed by law without reference to the assent of the obligor.

2. They are particular, as distinguished from universal, obligations. That is, they are imposed because of a special state of facts and in favor of a particular person, and do not rest upon one at all times and in favor of all persons.

3. They are based upon equitable considerations, but had their origin in the courts of law and are enforced by so-called legal remedies.

4. They require that the obligee shall be compensated, not for any loss or damage suffered by him, but for the benefit which he has conferred upon the obligor.

The first, second, and third characteristics serve, as will be seen in the following sections, to distinguish quasi contracts from contractual obligations, from the general obligation not to commit a tort, and from equitable obligations proper, respectively. The fourth characteristic governs the measure of recovery. This will be treated specifically in connection with various classes of quasi contracts hereafter to be considered. In this chapter it is only necessary to say that while in many cases of the receipt of property there is doubtless a moral obligation to make restitution in specie, and while equity frequently compels restitution in specie, the only obligation recognized and enforced at law is the obligation to make restitution in value, i.e. to pay the equivalent or the reasonable worth of the benefit received.2 This obligation, for the sake of convenient brevity and in order to distinguish it from the secondary obligation of the contractor or tort-feasor to compensate the injured party for the damages suffered by him, will hereafter be called the obligation to make restitution.

Yale Law Jour. 533. Treating judgments and certain statutory, official, and customary obligations as within the field, he defines a quasi contract to be "a legal obligation, not based upon agreement, enforced either specifically or by compelling the obligor to restore the value of that by which he was unjustly enriched."

1 For the classification of obligations as recusable and irrecusable and the division of irrecusable obligations into particular and universal, see Professor Wigmore's article, "The Tripartite Division of Torts," 8 Harv. Law Rev. 200, 201.

2 As to the primary obligation of one in default under a contract within the Statue of Frauds, see post, Sec. 96.