The Essential Properties of Marriage
Q: What are the essential properties of marriage?
A: This question can be answered in two ways:
The first way to answer the question is to explain the nature of the essential properties. The essential properties of marriage are those characteristics God intended for marriage and without which there can be no marriage. Partners contracting a sacramental marriage must be open to these properties or no valid marriage is contracted.
A person does not have to consciously embrace the essential properties, but if he or she rejects them in such a way that this rejection “determines the will” then the union is invalid from the very beginning. That is, if a person says, “I will get married, but only of the condition that this characteristic will not be part of the union” then the marriage never comes into existence because the person has refused to enter the union that God’s defines as marriage.
The second way to answer the question is to enumerate the essential properties. Thus the Catechism of the Catholic Church states:
1664 Unity, indissolubility, and openness to fertility are essential to marriage. Polygamy is incompatible with the unity of marriage; divorce separates what God has joined together; the refusal of fertility turns married life away from its “supreme gift,” the child (GS 50 # 1).
Note that the third essential property of marriage is only openness to fertility, not fertility itself. Due to unfortunate circumstances, such as sterility, a couple may be unable to have a child, but still they may marry being open to fertility if God chooses to overcome their infertility or place them in a circumstance in which they conceive a child.