Consent is the deliberate agreement required of those concerned in legal transactions in order to legalize such actions. Words, deeds, writing, or silence hear witness to the existence of this consent. Completeness of consent is gauged not so much by the preliminaries of transactions as by their ratification, which is the psychological development of incipient consent, and gives consistency to legal transactions. The consent necessary to constitute contracts must be internal, external, mutual, and deliberate. Some authorities claim that contracts formed without any intention on the part of the contracting parties to oblige themselves are valid; others more rightly maintain the contrary, since the very essence of contracts embodies obligation. Consequently, whoever is unprepared to admit this obligation is in no position to make a contract. Two possible suppositions here present themselves. In the first the promise and intention of not assuming any obligation concern the same object under the same respect. Promises made in this way are utterly meaningless. In the second supposition the promise and intention of waiving the obligation refer to the same object under different respects. In such cases it is necessary to ascertain which of these two contrary tendencies of the will is dominant. If the intention of making a contract possess greater efficacy, the obligation thereunto corresponding unquestionably holds good. On the contrary, if the intention of accepting no obligation prevail, no contract can be formed. Finally, if one intention is just as efficacious as another, the formation of a contract would then involve quest for an unattainable result. Contracts made by individuals having absolutely no intention of abiding by the obligation connected therewith are altogether invalid, and the parties thus fictitiously contracting are bound to indemnify those whose interests thereby suffer. The contract in question must always be capable of begetting an obligation. It is not impossible to find genuine consent which is worthless for giving consistency to contracts either because it is nullified beforehand by positive law or because it is the result of error, fraud, or fear (see CONTRACT).
Error affecting the very nature of the contract, or concerning the substance of the object in question or a naturally substantial quality of the object, or one considered indispensable by the contracting parties, vitiates consent and invalidates contracts. Error regarding an accidental quality of the contract, or pertaining to the motive underlying the contract, or to its material object, is insufficient to vitiate consent or nullify contracts. In like manner fraud, whether introduced by one of the contracting parties or by an extern, for the sake of provoking consent in the other party, counteracts consent as often as such fraud circumscribes the nature of the contract, the substance of the object at stake, or a quality naturally substantiated in that object or esteemed as substantial by the one upon whom the fraud is perpetrated. As often as accidental fraud induces another, in some measure, to consent, he is at liberty to rescind the contract, provided it is naturally dissoluble. In general, grave fear lawfully superinduced does not militate against consent in the will, and therefore renders contracts neither invalid nor rescindable. On the other hand, while fear unlawfully superinduced to extort consent does not invalidate contracts, it gives the intimidated party the liberty of rescinding them. According to the civil law of the United States, no contract is binding without the mutual assent of both parties. They must assent at the same time and to the same thing. This mutual assent consists of an offer by one party and its acceptance by another. When the offer is verbal, and the time allowed for acceptance is not mentioned, the offer must be immediately accepted to constitute a contract. In case the offer and acceptance are written and pass through the mail, the contract is complete when the acceptance is mailed, provided the party accepting has received no notice of the withdrawal of the offer before mailing his letter. As far as the validity of matrimony is concerned, genuine, internal, personal consent of both parties, covering the present and indicated by external signs, is unquestionably required. While internal consent must be complemented by some external manifestation, words are by no means necessary. The Congregation of the Inquisition (22 August, 1860) decided that marriages are entirely valid when the ceremony takes place in the presence of witnesses and according to the custom of the country in a manner which indicates that the contracting parties here and now mutually agree to enter wedlock. At the same time, if one or both contracting parties have no present intention of marrying in circumstances such as those outlined, they can make no marriage contract. The required matrimonial consent signified by proxy does not militate against the validity of the marriage contract. This consent must include the material object of the matrimonial contract, which material object is the mutual right of one party to the body of the other, a right that carries with it every prerogative vested therein by the laws of nature. It is not necessary, however, that the intention of parties to a marriage contract should be explicitly directed to all its conditions or circumstances. On the contrary, an intention implicitly thereunto directed is entirely sufficient for all practical intents and purposes. Hence, as often as marriageable parties intend to contract marriage in the way in which men and women ordinarily understand that agreement, or according to the way in which it was instituted by the Author of this sacrament, they exhibit consent sufficient to render their marriage contract entirely valid, provided nothing essential is positively excluded by a counter intention usurping the place of the chief, indispensable intention in entering matrimony. While marriage contracts are null unless based on the consent of those concerned, it is usually very difficult to establish the actual absence of this consent so as to satisfy the judge in a matrimonial court, once the marriage ceremony has really taken place. (For the renewal of consent in the case of invalid marriages, see REVALIDATION, and for the consent requisite for espousals, see ESPOUSALS.) While in canon law the consent of parents is not necessary to validate the marriages of their children, it is usually required to render such marriages legitimate. For the [civil law concerning the consent of parents in France (modified 1907), Germany, Austria, Switzerland, Canada, etc., see MARRIAGE.]
In the United States the common law exacts no solemnity to validate matrimonial consent. In many of the States, however, special statutes carrying a penalty require certain conditions for the legitimacy of such consent. Common law regards marriage as a civil contract for which consent alone is essential. It demands no legal forms, nor religious solemnities, nor special mode of proof. According to common law, consent indicated by words covering the present, whether consummation follows or not, or by words pertaining to the future together with consummation, constitutes a valid marriage. In New York, Illinois, and Rhode Island words pertaining to the future, even with subsequent consummation, no longer render a marriage valid. Even without explicit proof of words implying consent, cohabitation, acknowledgment of a marriage by the parties concerned, reception of such parties as husband and wife by relatives, friends, or society, are sufficient to establish a valid marriage.
Canon law requires the consent of cathedral chapters to lend validity to certain official acts of bishops. In general, this consent is necessary in such matters as usually involve a serious obligation or the possibility of a notable damage, or in matters which simultaneously pertain to bishops and their chapters. Nevertheless, unwritten law can narrow the rights of chapters and widen the liberty of bishops in these matters unless circumstances conspire to stamp particular measures as unreasonable. In like manner, unwritten law may exact the consent of chapters in matters of secondary importance, a requirement sometimes enjoined by special statutes. When immediate action is necessary, and it is impossible to convoke their chapters, bishops may proceed validly without the chapters' consent. Inasmuch as there are no cathedral chapters in the United States diocesan consultors constitute the advisory board of the bishops. The Third Plenary Council of Baltimore specifies several instances in which the bishops, though not obliged to abide by the advice of their consultors, are bound to seek such advice, else their acts in such cases are liable to nullification.
For consent in its relation to sinful acts, see SIN, and for the consent of the legislative authority in the formation of consuetudinary law, see CUSTOM.