In the 15th Century the Roman Catholic Church invented the idea of mortal and venal sins. Mortal sins imperil one’s soul and venial sins are less serious breaches of God’s law. The Catholic Church believes that if you commit a mortal sin, you forfeit heaven and opt for hell by your own free will and actions. Three conditions are necessary for mortal sin to exist:
Grave Matter: The act itself is intrinsically evil and immoral. For example, murder, rape, incest, perjury, adultery, and so on.
Full Knowledge: The person must know that what they’re doing or planning to do is evil and immoral.
Deliberate Consent: The person must freely choose to commit the act or plan to do it. Someone forced against her will doesn’t commit a mortal sin.
Confusion within Catholic circles exists as to whether divorce is a mortal sin or a venal sin and many believe that some divorce actions fall under mortal sin and some do not. Many believe that a divorce is a venal sin but remarriage is a mortal sin. Of course the entire construct of mortal and venal sins is man-made, and the Bible does not refer to divorce as a sin at all. According to God’s word divorce is a provision of God’s law to protect the innocent spouse from a treacherous partner, and no, Jesus did not abrogate this provision in God’s law. Catholics and Protestants alike have lost sight of this biblical reality. Regardless of the doctrinal positions on marriage and divorce, most seem to believe that venal sins are involved when a spouse breaks the conditions of the marriage covenant, and a mortal sin is committed when the innocent spouse moves to dissolve the broken marriage covenant via divorce. This superstitious viewpoint is a remnant from the 2,000 year history of theologians arguing over these issues. The biblical understanding is diametrically opposed as the breaking of the marriage covenant’s conditions is a sin against God and a crime against one’s spouse and Jesus made it clear that such crimes make allowance for a divorce for the benefit of the innocent spouse. Divorce does not break the marriage covenant, but it is God’s gracious provision for cases where one spouse has already broken the marriage covenant by breaking one or more of the marriage covenant’s conditions.
The first inclusion of marriage among the seven sacraments of the New Law by the Church’s magisterium occurred at the Council of Verona in 1184. This man-made doctrine of the sacramental marriage preceded and, in large part, brought about divorce being labeled a mortal sin. These two man-made doctrines were never entirely overturned during and after the reformation (formally they were, but the implications of these man-made doctrines continued a life of their own). Consequently, both of these concepts are deeply embedded in the Christian psyche to this day even though they have been, more or less, formally rejected.