Agreements that fell in none of these four classes were simple pacts (pacta), not contracts, and were not actionable. Such pacts might, how ever, be available for defense, e.g. when a credi tor had given his debtor an informal release or an extension of time, and pacts made immediately after the conclusion of a eontract (pacta adierta) were treated as part of the contract.
In order that a contract should be valid it was necessary that the parties should be of such age as to be callable of binding themselves, and of sound mind. and that the object to be attained should be neither impossible, illegal, nor immoral. Mistake (error) was regularly fatal to the valid ity of a contract. provided the mistake was ex cusable and essential. A mistaken reason or motive for contracting was not regarded as essen tial. Where, however, the mistake was caused or utilized by the other party, these limitations disappeared and the contracts were voidable for fraud (do/us). Duress (metus) also made a con tract invalid.
To modern European codes, all agreements ex cept those looking to impossible or immoral ends are valid and actionable, unless a special form is required by law and the required form has not been observed. It is therefore maintained by many
writers that the Itoman category of real contracts has disappeared, and that there are now but two classes, the formal and the consensual. The formal contracts of the modern codes arc not Roman. Where a form is prescribed, it is usually a written document, and in many eases attesta tion by a notary is necessary to its validity.
BIBLIOGRAPHY. For special branches consult the Bibliography. For special branches consult the authorities referred to under the titles treating of those subjects. as REAL PROPERTY; SALE; Mokro.xoE, etc. Also consult: Parsons. Law of Contracts (8th ed., Boston, 1893 ) ; Anson, Prin ciples of the haw of Contract (7th ed., Oxford, 1893; 2d _American ed.. Chicago, 1887) ; Chitty, Treatise on the Law of Contracts (13th ed., Lon don, 1896) ; Addison, Treatise on the Law of Contracts (7th cd., London, 18931: Marriman, Elements of Contracts (2d ed., Boston, 1901) ; Hollingsworth, The Lute of Contracts (189(1) ; and the authorities referred to under such special titles as QUASI CONTRACT; NEGOTIABLE INSTRU MENTS; SALE, etc.