The canonical process of nullity of marriage by psychology and using the available evidence leads to objective truth about the challenged marriage. A variety of factors that affect the personality of a person can make him or her incapable of taking up marriage. The Legislator in one of the canons pointed to mental disorders as a possible cause of marriage nullity. It is important to show the genesis of the canon, its purpose and the matters for which it was established. It is also necessary to identify specific personality disorders that make the inability to marry. The purpose of this article is to draw attention to the fact that the Church’s doctrine concerning the indissolubility of marriage or the existence of “divorce” does not change. The whole of canonical conduct in matrimonial matters is in the first place the good of man and the truth about the indissolubility of marriage.