(b) The ends of the contract are, primarily, the good of the race and of the children, and secondarily the good of the couple through mutual assistance and protection in spiritual and temporal matters. To these general ends may be added others which a particular person has in view, such as dignity, wealth, honor, lawful pleasure.
(c) The essence of the contract is the consent, for every pact consists in mutual agreement. But if marriage be regarded as a permanent state, its essence is the bond of union, and consent is the efficient cause productive of the bond. Marriage consent must have the qualities (internal, external, mutual, free) that are necessary in every contract, as explained in 1883.
2790. Requirements for Valid Marriage Consent.—(a) Internal Consent.—If both or one of the parties internally and positively wills to exclude marriage, or the right to the conjugal act, or an essential property of marriage, the contract is null, since there is no purpose to contract a real marriage. Similarly, if both or one of the parties negatively (or by lack of all intention) excludes consent, there is no marriage. It should be noted that he who intends to get a divorce later on does not intend a permanent union or marriage, whereas he who intends to be unfaithful or to practise onanism may nevertheless intend to oblige himself to the duties of fidelity and of the lawful use of marriage, and therefore to a true marriage. Fictitious consent, unless a serious reason excuses (e.g., when one is forced under grave fear to marry, when one becomes aware of a diriment impediment at the altar and cannot retire without great scandal), is a mortal sin, as being a lie in a very important matter and an injustice. If the other party was deceived, the party guilty of feigned consent is bound to make reparation for the damage done, and, unless the marriage has become impossible or inadvisable, the means of reparation should be a genuine consent revalidating the marriage. This is especially true when there is a conflict between the internal and the external forums on account of the inability to establish juridically the nullity of the invalid marriage.
(b) External Consent.—Both as contract and as Sacrament, matrimony requires some sensible manifestation of the internal consent. Since the contract of marriage between Christians falls under the jurisdiction of the Church, the manner of expressing the consent is regulated by Canon Law. The solemnities required for valid and lawful marriage will be treated below in 2826, 2827.
(c) Mutual Consent.—Both parties must agree to the marriage, since no one is obliged by a contract without his consent. But mutuality does not imply simultaneity, for, if the previous consent given by one party continues, the subsequent consent given by the other is joined to it and the consent becomes mutual.
(d) Free Consent.—If every contract must be deliberate and voluntary, this is especially true in the case of marriage, since it entails very heavy duties and its obligations are lifelong (cfr. 2195). In marriage there must be full and perfect consent, though it is not necessary that one think expressly on the essentials of the contract when assenting to it.
2791. Defects in Consent.—Consent supposes sufficient knowledge, and hence it may be vitiated by a defect as to knowledge.
(a) Mental Derangement.—Those who are not in possession of their mental faculties cannot marry, whether the derangement be habitual (e.g., idiots, the completely insane, monomaniacs on the subject of marriage) or actual (e.g., infants, those who are completely drunk or doped, the hypnotized or delirious, somnambulists). But defectives who are not unbalanced all the time or on all subjects, may be able now and then to realize the meaning of marriage and to give deliberate consent, though the presumption is against them. Those whose mentality is of a low grade, but who are able to judge and reason correctly (e.g., stupid persons, the deaf and dumb, or blind), and those who have some little fanaticism or eccentricity are not excluded; otherwise very few of either sex could marry.
(b) Ignorance.—Substantial ignorance, or the absence of knowledge about the essentials of marriage (viz., that it is a permanent association of man and woman for the purpose of raising children of their own), makes the contract null, for one does not consent to what one does not know. Accidental ignorance, on the contrary, does not nullify, for he who understands the main facts about marriage can intend to contract it as others do, even though he does not know its details or secondary features. Ignorance invalidates marriage, therefore, if one of the parties does not know that marriage is meant for the procreation of children or that children are procreated by carnal intercourse; but it does not invalidate if the parties are ignorant about physiology or scientific explanations. Substantial ignorance in persons of marriageable age (especially young women) is not uncommon even in these days, but it is not presumed after puberty (Canon 1082, Sec.2).
(c) Error.—Error which excludes consent to the essential object of the contract nullifies, and hence a substantial error about the person with whom one is contracting makes marriage of no effect (e.g., if Titus thinks he is marrying Claudia, but is really marrying her twin sister, Sempronia; if Balbus intends to marry Caia only on condition that she is a virgin and she is not a virgin; if Julius intends to marry the woman who is present solely as differentiated by a personal or individual characteristic which he mistakenly believes her to have, such as seniority among her sisters). Error which does not prevent essential consent does not nullify the contract. Hence, a mere accidental error about the other party (e.g., Titus marries Claudia, thinking she is rich, whereas she is poor, and he would never have married her had he known her poverty) does not make marriage null, though the Church makes the marriage of no effect when a slave is married in the belief that he or she is free (Canon 1083, Sec.2, n, 2). A mere speculative error about the properties of marriage (e.g., if one believes that marriage may be lawfully dissolved for adultery) or about the validity of one’s own marriage (e.g., if the bride erroneously believes that the marriage she is contracting is null) does not deprive the contract of its force, if there is really a purpose to marry as best one may; for such an error does not act upon the will or take away consent.