BITE-SIZE THEOLOGY (159) What deficiencies in knowledge and consent can affect the marriage?

Rev José Mario O Mandía 

Since free consent depends on an act of the intellect and the will (cf CCC 1731), we can say that anything that either diminishes (1) the knowledge required or (2) the exercise of the will negatively affects the consent. 

(1) Knowledge can be deficient either because of (1.1) mental incapacity, or (1.2) ignorance, or (1.3) error in judgment.


“The following are incapable of contracting marriage:

1. those who lack sufficient use of reason;

2. those who suffer from a grave defect of discretion of judgment concerning the essential matrimonial rights and obligations to be mutually given and accepted;

3. those who, because of causes of a psychological nature, are unable to assume the essential obligations of marriage” (CCL, canon 1095).


Canon 1096 explains what the contracting parties must know regarding marriage: 

“Section 1. For matrimonial consent to exist, the contracting parties must be at least not ignorant that marriage is a permanent partnership between a man and a woman ordered to the procreation of offspring by means of some sexual cooperation.

Section 2. This ignorance is not presumed after puberty.”


Ignorance is absence of knowledge. 

Error already implies having some knowledge but making the wrong judgment.

“Can. 1097

Section 1. Error concerning the person renders a marriage invalid.

Section 2. Error concerning a quality of the person does not render a marriage invalid even if it is the cause for the contract, unless this quality is directly and principally intended.”

There is “error concerning the person” (Section 1) “when the contracting party, wanting to marry a determined person, marries someone else by mistake” (E Caparros, M Thériault, J Thorn, Code of Canon Law Annotated, 3rd ed, p 841).

“Can. 1098. A person contracts invalidly who enters into a marriage deceived by malice, perpetrated to obtain consent, concerning some quality of the other partner which by its very nature can gravely disturb the partnership of conjugal life.”

“Can. 1099. Error concerning the unity or indissolubility or sacramental dignity of marriage does not vitiate matrimonial consent provided that it does not determine the will.

“Can. 1100. The knowledge or opinion of the nullity of a marriage does not necessarily exclude matrimonial consent.”


“Can. 1101

Section 1. The internal consent of the mind is presumed to conform to the words and signs used in celebrating the marriage.

Section 2. If, however, either or both of the parties by a positive act of the will exclude marriage itself, some essential element of marriage, or some essential property of marriage, the party contracts invalidly.”

“Can. 1102

Section 1. A marriage subject to a condition about the future cannot be contracted validly.

Section 2. A marriage entered into subject to a condition about the past or the present is valid or not insofar as that which is subject to the condition exists or not.

Section 3. The condition mentioned in §2, however, cannot be placed licitly without the written permission of the local ordinary.”

Finally, let us cite once more Can. 1103: “A marriage is invalid if entered into because of force or grave fear from without, even if unintentionally inflicted, so that a person is compelled to choose marriage in order to be free from it.”