God instituted marriage so that men and women might complete one another and share in his creative work through the procreation of children. Physical union in marriage has a spiritual significance in that it points beyond itself to the total unity of husband and wife, which is essentially a spiritual union. But to maintain its holiness this union must take place in a relationship committed to enduring exclusiveness. If you have another relationship while still married another person is selfishly exploited. What should be a constructive relationship serving as the means to deeper interpersonal communion becomes in promiscuous relationships destructive both to one's capacity for personal unity with a member of the opposite sex and to existing marriage relationships, if any.
Marriage relegates other human ties to a secondary role.
Spiritual and emotional satisfactions formerly drawn from the parental relationship the marriage partners are now to find in one another. To sunder one's parental relationships and join oneself in intimate, lifelong union with a person who hitherto has been a stranger demands a considerable degree of maturity, as expressed in a capacity for self-giving love, emotional stability, and the capacity to understand what is involved in committing one's life to another in marriage. Marriage is for those who have grown up. This is not possible in a social system in which either men or women are not accorded full human dignity. Not at all, for this doctrine refers to a hierarchy of function, not of dignity or value.