I have been looking again at Georges Dubys theories about the two medieval models of marriage (in Medieval Marriage: Two Models from Twelfth-Century France (1978) and The Knight, the Lady and the Priest: the Making of Medieval Marriage in Medieval France (1983) and coming to the same conclusions as before: it doesnt fit the Carolingian evidence. As far as I can tell, no-one has yet demolished Dubys argument for the twelfth century (though I think there are some holes), so the question becomes: what changed from the ninth century and why?
Dubys main argument starts from the opposed aims of marriage for laymen (dynastic) and clerics (holy), which results in a wish for different rules on marriage. The three main oppositions are often said to be endogamy v exogamy, control of marriage by families v consent of couple and easy divorce v very limited divorce.
The biggest hole in Dubys argument is that while it may be possible to argue that there is a church viewpoint (given that the period is a time of increasing papal control and the development of systematic canon law), its very hard to argue that there is a lay viewpoint (even if you restrict it to the high nobility of France). Thats because the wishes of noble laymen are deeply contradictory about what they want from marriage. For example, its misleading to say that lay nobles wanted endogamy and that this was in order to preserve property intact. To preserve patrimonies in this way, you really need men to be marrying their nieces or first cousins, and there is very little evidence for such close endogamous marriage in either the early or Central Middle Ages (with the exception of Catalonian counts). In a endogamous society, moreover, youre expected/encouraged to marry your cousin etc. Its more accurate to say that what nobles wanted was the possibility, but not the necessity of marrying a distant relative, if it was helpful.
Similarly, parental control of marriage is something that broadly noble parents want, but their noble children (particularly adult sons) dont want. Heiress hunting and other forms of male hypergamy are far more practicable if you only have to get the consent of the woman and not her family. Even easy divorce, which seems an obvious benefit for laymen, isnt necessarily so – its a problem if your favourable marriage or that of your daughter is broken up by the in-laws. In a sense, what laymen really want is tight rules for everyone but themselves: no divorce but theirs, no consanguinous marriage but theirs, parental consent to all marriages, when theyre the father.
If the clerical model of marriage came to be broadly accepted, at least in theory, by twelfth century noblemen, as Duby rightly claims, it was probably because in practice there were compromises and loopholes in church law which allowed the lay model of marriage to continue. Papal marriage dispensations, for example, provided precisely a way of laymen marrying their distant relatives and divorcing them if needed. Similarly, the church was often prepared to assume consent by the couple unless they kicked up a fuss.
The same tendency to compromise seems to me to be there in the Carolingian period, but in crucially different areas. Firstly, the early medieval church, when it referred to the need for consent to make a marriage, very rarely meant that only the couples consent was needed. Almost always, consent by the families was also needed, which is why the crime and sin of raptus included elopement as well as abduction.(There may have been slightly more leeway for widows). In that respect, the Carolingian church stuck firmly to the lay model.
Secondly, while the limits on consanguineous marriage didnt change between the ninth and twelfth centuries, the practicalities did. (The argument that there was a change over from Roman to Germanic ways of counting degrees in the Gregorian reforms doesnt hold up). Carolingian councils sometimes said no marriage within three degrees, some four degrees, sometimes five, sometimes six or seven, but sometimes as far as relationships were known. But in practice, once you get to four degrees or beyond these probably all boiled down to much the same thing, because in a society almost entirely without written genealogies and relying on oral tradition, four degrees is as much as anyones likely to know (and three is more common). (Early medieval royal genealogies/kinglists may seem to be an exception to this, but in fact arent really, because they remember only male-line descent and so ignore 90% of relatives.)
In other words, based on oral culture, you might just know who your grandparents grandparents were (four generations back), but further back is almost certainly unrealistic, so that the most distant relatives you might know about are your third cousins. (As a parallel I would say, roughly speaking, that except in very close-knit societies, most modern people in the West are close to their siblings (1st degree), know their first cousins (2nd degree) and know of their second cousins (3rd degree). So not marrying your (known) relatives and not marrying anyone within 4+ degrees is much the same in Carolingian society.
What changes is the practice of recording detailed (not just selective) genealogies, which seems to have taken off for nobles only from the eleventh century. (Duby in The Chivalrous Society refers to one example in France from before then). The condemnations of consanguinous marriage seem to have encouraged the drawing up of such charts and, once theyd been recorded in writing, they could be extended into further generations. In other words, it began to be possible for nobles, at least, to know who their fifth degree relatives were, rather than have a convenient ignorance. This change also meant a shift of power over who decided on marriages: control went to whoever drew up the genealogies and used them. In the Carolingian period, in contrast, (and this is made explicit in at least one case), it is the memory of the elders that is decisive. In other words, the restrictions gave a chance for any of the parents of the couple (and the elderly relatives more generally) to say: They cant get married because I remember my granny saying she was related… without fear of contradiction by the couple themselves. The rules therefore benefited lay seniores at the expense of iuniores: its no wonder that the magnates themselves endorsed it.
The most potential for conflict between different views of marriage in the Carolingian period was on how easy divorce should be. Why did Carolingian laymen (at least in theory) accept the principle of indissolubility? Here, I think you have to say that the church did in theory win out. It was harder for Carolingian kings than Merovingian or Capetian kings to get divorced. Unlike in the later periods that Duby sees, there are few examples of kings or nobles blatantly defying church rules on indissolubility. Instead, you see persistent attempts to game the system, whether in the infinite excuses of Lothar II or slightly further down the social scale, in men, for example, who claim that they were never properly married in the first place. I can only presume that, as in other cultures where divorce has been almost completely prohibited, enough wiggle room was left for remarriage in practice, while creating a important new holy facade.
So does this mean that you can accept the principle of lay and clerical models for marriage in the ninth century and just say the parameters have changed slightly? I dont think you can. What you seem to me to have is in many ways an overlapping viewpoint: marriage as monogamous and exogamous and controlled by the family, relatively limited divorce. The differences are at the edges: how much exogamy, when is divorce possible? You dont get a very different view in the sources written by or for laypeople and those written by or for clerics, as with Dubys evidence. Id say its less two models than one lay model being pulled in a slightly new direction by some clerics. In which case the real change in the eleventh century is a generation of churchmen refusing to make such compromises, but instead insisting on their own view of marriage (and the power of the church to decide on such matters).