Luther: Christians Are Allowed to Marry Their Nieces?

Here's one from the Catholic Answers Forums concerning marriage and the degrees of consanguinity:

...why would Luther feel compelled to write about marriage and challenge/refute so much of what had been considered Christian marriage for centuries? Do we as modern day Christians think he was right about Christians being allowed to marry our nieces, or do we feel that Luther was way off base here? Did this nuttiness have an impact on the culture? You bet it did.

These questions were asked along with the posting of Luther's The Persons Related By Consanguinity and Affinity Who Are Forbidden To Marry According To Scriptures, Leviticus 18 (LW 45:3-7) was posted. Marriage in the 16th Century was a complicated topic, and these questions / conclusions appear to be based on Luther writing "From this it follows that with a good conscience before God I may marry the child of my brother or sister, or my stepmother's sister" found in the link above.

The simple answer to the above questions is that the Roman church had developed an entire legal system from the preceding centuries, particularly with the development of canon law during the late eleventh through thirteenth centuries.  Canon law had determined which people could marry, and often these rules had no scriptural basis. Luther sought to define whom was allowed to marry based on Scripture (i.e., Leviticus 18). The important question to ask is not whether or not Luther was "off  base" or engaging in "nuttiness," but rather whether or not (or to what degree) a society should follow Levitical law in defining marriage. If one should not keep Levitical law, isn't that saying that one is allowed to basically marry anyone?  Certainly Luther was not in favor of keeping the law of Moses. On the other hand, Luther saw that the laws in Leviticus 18 set up natural law guidelines for marriage. In a letter commenting on Lev. 18:16, Luther states:

You will reply: If someone continues this argumentation then he will end up teaching that we also are not prevented by any law of God from marrying daughters, sisters, or mothers, since the law of Moses prohibits this, but the law of Moses now no longer binds us Gentiles. I answer that such marriages are prohibited and considered incestuous by natural law. This is sufficiently proven by the fact that in Scripture before, during, and after [the time in which] the law [of Moses was valid,] no example [for the permission of such marriages] can be found, and without example and law nothing may be undertaken. Precisely by this fact God has sufficiently demonstrated that he condemns such marriages. But there are laws and examples for marrying your deceased brother’s wife. (LW 50:37)

When Luther says, "From this it follows that with a good conscience before God I may marry the child of my brother or sister, or my stepmother's sister," he's basing his conclusion on an interpretation of Leviticus 18.  Luther elsewhere reasons,

The first impediment is blood relationship. Here they have forbidden marriage up to the third and fourth degrees of consanguinity. If in this situation you have no money, then even though God freely permits it you must nevertheless not take in marriage your female relative within the third and fourth degrees, or you must put her away if you have already married her. But if you have the money, such a marriage is permitted. Those hucksters offer for sale women who never have been their own. So that you can defend yourself against this tyranny, I will now list for you the persons whom God has forbidden, Leviticus 18[:6–13], namely, my mother, my stepmother; my sister, my stepsister; my child’s daughter or stepdaughter; my father’s sister; my mother’s sister. I am forbidden to marry any of these persons. From this it follows that first cousins may contract a godly and Christian marriage, and that I may marry my stepmother’s sister, my father’s stepsister, or my mother’s stepsister. Further, I may marry the daughter of my brother or sister, just as Abraham married Sarah. None of these persons is forbidden by God, for God does not calculate according to degrees, as the jurists do, but enumerates directly specific persons. Otherwise, since my father’s sister and my brothers daughter are related to me in the same degree, I would have to say either that I cannot marry my brother’s daughter or that I may also marry my father’s sister. Now God has forbidden my father’s sister, but he has not forbidden my brothers daughter, although both are related to me in the same degree. We also find in Scripture that with respect to various stepsisters there were not such strict prohibitions. For Tamar, Absalom’s sister, thought she could have married her stepbrother Amnon, II Samuel 13[:13] (LW 45:22-23).

The first question being asked above is in regard to why Luther engaged the subject of marriage rather than just leaving the established medieval order alone. This question was answered in a thoughtful essay, John Witte, The Reformation of Marriage Law in Martin Luther's Germany: Its significance Then and Now (Journal of Law and Religion, Vol. 4, No. 2 (1986), pp. 293-351.

According to many contemporary observers, Luther's alarm over the decrepit estate of marriage and marriage law was certainly not unfounded. Germany suffered through decades of indiscipline and immorality in the late fifteenth and early sixteenth centuries. Prostitution was rampant. High clerics and officials of government regularly kept concubines and visited the numerous brothels in German cities. The small fines incurred for such activity discouraged few. Drunken orgies were commonplace. Women were raped and ravaged,particularly by robber bands and soldiers. Lewd pamphlets and books exalting sexual liberty and license were published with virtual impunity. Writings by some Roman Catholics extolling celibacy and deprecating marriage and sex dissuaded many couples from marriage and persuaded many parents to send their children to monasteries and cloisters. The number of single men and women, of monasteries and cloisters, of monks and nuns reached new heights in the years shortly before the Reformation. Within the estate of marriage itself, instances of bigamy, incest, and polygamy appeared with alarming frequency. The canon laws governing the formation and dissolution of marriages were flouted or arbitrarily enforced in several parts of Germany. Laws prescribing care and education of children as well as laws proscribing abortion, abuse of family members, adultery, and desertion were regularly violated. Calls such as Luther's for the reformation of marriage and marriage law and for the reinforcement of public morality were therefore received sympathetically by Roman Catholics and Protestants alike.
Unlike the Roman Catholics, however, Luther and other German Protestant reformers attributed much of the decay of marriage not only to the negligence and arbitrariness of authority and the moral laxness of society but also to the canon laws of marriage and the Roman Catholic theological concepts of marriage underlying these laws. For the reformers the canon law of marriage yielded paradoxical results. It discouraged and prevented mature persons from marrying by its celebration of celibacy, its proscriptions against the breach of vows to celibacy, its permission to breach oaths of betrothal, and its numerous impediments. Yet it encouraged marriages between the immature by declaring valid secret unions consummated without parental permission as well as oaths of betrothal followed by sexual intercourse. It highlighted the sanctity and solemnity of marriage by deeming it a sacrament. Yet it permitted a couple to enter this holy union without clerical or parental witness, instruction, or participation. Celibate and impeded persons were thus driven by their sinful passion to incontinence and all manner of sexual deviance. Married couples, not taught the Scriptural norms for marriage, adopted numerous immoral practices. Such paradoxical results, the reformers averred, were rooted in tensions within the Roman Catholic theology of marriage. Although Roman Catholic theologians emphasized the sanctity and sanctifying purpose of the marriage sacrament, they nevertheless subordinated it to celibacy and monasticism. Although they taught that marriage is a duty mandated for all persons by divine natural law, they excused many from this duty through the restrictions of canon law. Both the Roman Catholic theology and the canon law of marriage thus met with sharp criticism on the part of the reformers.
First, many of the cardinal issues of the Lutheran Reformation were implicated by this doctrine and law. The Roman Catholic Church's exclusive legal authority over marriage was, for the reformers, a particularly flagrant example of the church's usurpation of civil legal authority. The Roman Catholic sacramental concept of marriage,on which the church had founded this authority, raised questions of sacramental theology and Scriptural interpretation. The numerous canon law impediments to marriage and prohibitions against complete divorce were in tension with the reformers' understanding of Scriptural norms for marriage. That a child could enter marriage without instruction or permission raised questions about the responsibilities of the family, church, and state to children. Issues of marriage doctrine and law implicated and epitomized the broader theological, political, and social issues of the Reformation. Thus it is not surprising that such a large number of German reformers-Luther, Melanchthon, Bucer, Brenz, Osiander, and numerous other theologians as well as Schiirpf, Monner, Kling, Lagus, Beust, Schneidewin, and many other jurists -debated these questions with such vigor(pp.293-296).

The Roman church had a complex set of these rules as well. The rules were set up in part as a way for the Roman church to nullify a consummated putative marriage:

Far more important were the diriment impediments used by the ecclesiastical courts to nullify even fully consummated putative marriages. One group of these impediments sought to preserve the freedom of consent of both parties. Thus a mistake about the identity of the other party nullified the marriage; mistakes about the social, financial, or civil status of the other were generally no longer considered to be grounds for nullification by the early sixteenth century. Extreme duress, fear, compulsion or fraud (by parents, spouses, or third parties) also impinged on consent and invalidated the marriage contract.
The canon law not only defined free consent but also specified which parties were free to give their mutual consent. Those who had made religious vows of celibacy or chastity in one of the sacred orders of the Church were eternally bound to God and thus could not bind themselves to another in marriage. Christians could not contract marriage with infidels, Jews, or pagans since the sacrament of baptism was a prerequisite for marriage; furthermore, such marriages could not symbolize the union of Christ with his faithful Church. Thus if a party departed from the faith after consummation and remained incorrigible, the Church could declare the marriage void. Persons related up to the fourth degree either to a common ancestor or to a couple (whether or not married) who had engaged in sexual relations were prohibited from marrying. These were called the impediments of consanguinity and affinity. Parents could not marry their adopted children or grandchildren, nor the spouses of their adopted children. One who baptized or confirmed a party or who became a godparent could not marry him or her; for these persons were considered to be the "spiritual fathers or mothers" of the party who received the sacrament.
The canon law also developed a group of impediments to protect the ultimate sanctity and function of the sacrament of marriage. First, conditions attached to marriage promises which were illegal or which were repugnant to the sacrament or harmful to the offspring automatically rendered the marriage contract void. Thus a promise with the condition "that we abstain for a season" was valid; but a condition "that we abort our offspring" or "that we permit each other sexual liberty with others" nullified the marriage contract. For such conditions vitiated the entire purpose of marriage: to unite together in love and to raise children in the service of God. Second, permanent impotence, insanity, or bewitchment of either party were generally grounds for nullification as well, provided that such a condition was latent before marriage, but unknown to the parties; if the parties knew of the condition before marriage or if it arose after consummation, they had no action for nullification. Third, the church annulled all bigamous and polygamous relations as contrary to the Gospel and to the purpose of marriage. Fourth, an unconsummated marriage could be annulled if one party severely abused or consistently threatened another with death, contracted a permanent contagious disease, or committed adultery. Where the marriage was consummated, however, the church permitted only a divorce, i.e., a judicial separation from bed and board. Divorce in the modern sense was not permitted; the sacramental bond, once consummated, remained indissoluble till the physical or civil death of one of the parties.(Witte, 305-306)

Luther expounded on his earlier rules of marriage in his treatise, The Estate of Marriage (1522) (LW 45). Here Luther directly comments on the rules of the church as they functioned in his day. Here are a few examples:

The second impediment is affinity or relationship through marriage. Here too they have set up four degrees, so that after my wife’s death I may not marry into her blood relationship, where my marriage extends up to the third and fourth degrees—unless money comes to my rescue! (LW 45:23)

The third impediment is spiritual relationship. If I sponsor a girl at baptism or confirmation, then neither I nor my son may marry her, or her mother, or her sister—unless an appropriate and substantial sum of money is forthcoming! This is nothing but pure farce and foolishness, concocted for the sake of money and to befuddle consciences. Just tell me this: isn’t it a greater thing for me to be baptized myself than merely to act as sponsor to another? Then I must be forbidden to marry any Christian woman, since all baptized women are the spiritual sisters of all baptized men by virtue of their common baptism, sacrament, faith, Spirit, Lord, God, and eternal heritage [Eph. 4:4–6].(LW 45:24)

The fifth impediment is unbelief; that is, I may not marry a Turk, a Jew, or a heretic. I marvel that the blasphemous tyrants are not in their hearts ashamed to place themselves in such direct contradiction to the clear text of Paul in I Corinthians 7[:12–13], where he says, “If a heathen wife or husband consents to live with a Christian spouse, the Christian should not get a divorce.” And St. Peter, in I Peter 3[:1], says that Christian wives should behave so well that they thereby convert their non-Christian husbands; as did Monica, the mother of St. Augustine. (LW 45:26)

The sixth impediment is crime. They are not in agreement as to how many instances of this impediment they should devise. However, there are actually these three: if someone lies with a girl, he may not thereafter marry her sister or her aunt, niece, or cousin; again, whoever commits adultery with a woman may not marry her after her husband’s death; again, if a wife (or husband) should murder her spouse for love of another, she may not subsequently marry the loved one. (LW 45:26)

The seventh impediment they call public decorum, respectability. For example, if my fiancée should die before we consummate the marriage, I may not marry any relative of hers up to the fourth degree, since the pope thinks and obviously dreams that it is decent and respectable for me to refrain from so doing—unless I put up the money, in which case the impediment of public decorum vanishes. Now you have heard a moment ago that after my wife’s death I may marry her sister or any of her relatives except for her mother and her daughter. You stick to this, and let the fools go their way. (LW 45:27)

The tenth impediment is condition of servitude. When I marry one who is supposed to be free and it turns out later that she is a serf, this marriage too is null and void. (LW 45:27)

There are still four more impediments, such as episcopal prohibition, restricted times, custom, and defective eyesight and hearing. It is needless to discuss them here. It is a dirty rotten business that a bishop should forbid me a wife or specify the times when I may marry, or that a blind and dumb person should not be allowed to enter into wedlock. So much then for this foolishness at present in the first part. (LW 45:30)