As has been said before,1 the term "contract" as used at Common Law included all rights which could be enforced by one of the actions ex contractu. By the Common-Law classification every contract was either express or implied, as these two classes exhausted the entire general class of contracts. If from all the rights of action which at Common Law could be enforced by actions ex contractu we subtract the rights arising out of express contract we have left a miscellaneous group of rights which the Common Law in its later and classic form grouped under the head of implied contracts. With the abolition of Common-Law forms of action in many jurisdictions, and its reconstruction on a rational basis in others, the necessity of defining such legal ideas as contract and tort without reference to the rigid form of action by which only it once was enforceable, has become apparent. Substantive law has been arranged and classified as the main division of the law, to which, in theory at least, the adjective law of pleading, practice, evidence, remedies, and procedure, is supplemental, whereas under the Common Law ideas substantive law was in reality a mere appendix and supplement to the law of procedure. The modern law, as has been said before,2 has treated the term "contract " as including all agreements which are enforceable at law. When we analyze the common law class of implied contracts and apply to it the modern test of what a contract is, we find that the Common Law class of implied contracts is made up of two distinct classes of rights. One class consists of rights arising out of an agreement enforceable at law, and therefore just as truly a contract at modern modern law as the express contract. It differs from the express contract only in this: that while in express contract the parties arrive at their agreement by words, whether oral or written, sealed or unsealed, in implied contracts of this type they have arrived at their agreement by their acts and conduct. This type of contract is known as the genuine implied contract, the contract implied as of fact, or simply, the implied contract. The other class of rights includes all the classes of rights in the Common Law class of implied contracts left after deducting all the rights which originate in a genuine agreement between the parties. To state the same fact in another way, it consists of all rights which the common law enforced by an action ex contractu, but which do not originate in a genuine agreement of the parties. This last class has been called contract implied in law, a contract created by law,3 constructive contract or quasi-contract. This type of liability is merely "an implication of law that arises from the facts and circumstances independent of agreement or presumed intention." 4 The term quasi-contract,

1See Sec. 11.

2 See Sec. 10-12, 14.

3 Bishop on Contracts, Ch. VIII.

4Pracht v. Daniels, 20 Colo. 100, 103; 36 Pac. 845. "There is some confusion in the statement of the law applicable to what are frequently called implied contracts, arising from the fact that obligations generally different have been classed as such, not because of any real analogy, but because where the procedure of the Common Law prevails, by the adoption of a fiction in pleading - that of a promise where none in fact exists or can in reason be supposed to exist - the favorite remedy of implied assumpsit could be adopted. This was so in that large class of cases, where suit is brought to recover money paid by mistake or has been obtained by fraud. Here it is said the law implies a promise to repay the money, when it was well understood that the promise was a mere fiction, and in most cases without any foundation whatever in fact. The same practice was adopted where necessaries had been furnished an insane person or a neglected wife or child. In all these cases no true contract exists. They are, by many authors, termed quasi contracts, a term borrowed from the civil law. In all these cases no more is meant than that the law imposes a civil obligation on the defendant to restore money so obtained, or to compensate one who has furnished necessaries to his wife or child, where he has neglected his duty to provide for while but little used in law is a term of considerable antiquity in English law. The term "quasi ex contractu" is used in Bracton5 to include " agency, wardship, the division of a common property, the distribution of an inheritance, an action arising out of a testament, a suit to recover a sum paid and not due, them, or, by reason of mental infirmity, is unable to obtain them for himself. But contracts that are true contracts are frequently termed implied contracts, as, where from the facts and circumstances, a court or jury may fairly infer, as a matter of fact, that a contract existed between the parties, explanatory of the relation existing between them. Such implied contracts are not generically different from express contracts; the difference exists simply in the mode of proof. Express contracts are proved by showing that the terms were expressly agreed on by the parties, whilst in the other case the terms are inferred as a matter of fact from the evidence offered of the circumstances surrounding the parties, making it reasonable that a contract existed between them by tacit understanding. In such cases no fictions are, or can be, indulged. The evidence must satisfy the court and jury, that the parties understood that each sustained to the other a contractual relation; and that by reason of this relation the defendant is indebted to the plaintiff for services performed or for goods sold and delivered. In the leading case of Hertzog v. Hertzog, 29 Pa. St. 465, the distinction is clearly stated by Judge Lowrie. After quoting from Blackstone, and observing that his language is open to criticism, he says: ' There is some looseness of thought in supposing that reason and justice ever dictate any contracts between parties, or impose such upon them. All true contracts grow out of the intentions of parties to transactions, and are dictated only by their natural and accordant wills. When the intention is expressed, we call the contract an express one. When it is not expressed, it may be inferred, implied, or presumed, from circumstances really existing, and then the contract thus ascertained, is called an implied one. . . . It is quite apparent, therefore, that radically different relations are classified under the same term, and this often gives rise to indistinctness of thought. And this was not at all necessary; for we have another well authorized technical term exactly adapted to the office of making the true distinction. The latter class are merely constructive contracts, while the former are only implied ones. In one case the contract is a mere fiction, a form imposed in order to adapt the case to a given remedy; in the other it is a fact legitimately inferred. In one the intention is disregarded; in the other it is ascertained and enforced. In one the duty defines the contract; in the other the contract defines the duty.' " Columbus, etc., Ry. v. Gaff-ney, 65 0. S. 104, 113; 61 N. E. 152; quoting Hertzog v. Hertzog, 29 Pa. St. 468.

5 Bracton f. 100b, Twiss's edition, Vol. II., 118.

and such like." We thus see that Bracton's classes of quasi-contract were much the same as those of modern law. It is classed with contract for the historical reasons already given even if the facts show affirmatively that there was no real agreement between the parties.6 There is still confusion of thought as to what implied contracts are. Thus it has been suggested that a genuine agreement, reached not by means of express words but by means of acts and conduct, is an express contract and not an implied contract.7 In discussing genuine implied contracts, the questions usually presented are what presumptions of law arise on the facts in evidence, or what inferences of fact will the law permit to be drawn therefrom. In constructive contracts the questions usually presented are, (1) under the facts does any liability of the defendant to the plaintiff exist; and further, (2) if there is a liability, can it be enforced in an action ex contractu. The latter question is of little importance to-day in jurisdictions where the Common Law forms of actions have been abolished. If facts appear giving a right to recover for money had and received, a fictitious promise need not be alleged.8

6"It must be remembered, that the promise upon which the action rests, is not the direct act of the parties, but a promise which the law implies from the facts, on the theory that a party is willing and undertakes to do what he ought to do. It does not militate against the promise which the law implies that the facts are inconsistent with the intent or promise to pay over. . . . While it may seem illogical for the law to imply a promise on the part of one whose conduct and declarations clearly disprove any intention to promise, still it is constantly done. It is one of the fictions of the law which it seems convenient, if not necessary, to retain until the courts adopt the doctrine that such contracts are created by law, rather than implied by it." Siems v. Bank, 7 S. D. 338, 342; 64 N. W. 167.

7"Express contracts which are proved by the declarations and con-duct of the parties and other circumstances, all of which are explainable only upon the theory of a mutual agreement, are often called, although not with entire accuracy, implied contracts; and this distinction will explain the ambiguity of some authorities and the apparent contrariety of others." Hinkle v. Sage, 67 O. S. 256, 263; 65 N. E. 999.

8Waite v. Willis, 42 Or. 288; 7C Pac. 1034.