Can't we use the medieval situation as a proto-caste system, that would during the middleages (and after) slowly grow into a more Indian like caste system?
I doubt it : feudality social division was build on social mobility originally. Knights being issued from peasantry, social concurrence passing trough liberation of serves, inclusion of bourgeoisie, warring elite replacing landed elite, etc.
Basically, with a social rigidification, you won't probably have a feudal society to speak of.
OTL it almost happened (theoretically if not in practice) at least in France when around the An Mil several theologians, specially the bishops Gerard of Cambrai and Adalberon of Laon, resurrected the 3 'functional' classes of the Gallic society described by Caesar (druids, 'knights' / noble warriors, freemen, closely corresponding to the brahmins, kshatriyas and vaishyas) as the 3 'orders' structuring the society: Orantes, Pugnantes, Laborantes: 'those who pray', 'those who fight', 'those who work'.
1) Again, the division in three orders wasn't comparable to Indian.
I happen to own the book you quote, and there is the translation of the part were Duby mentionds that.
Page 14, P.U.F. edition.
It is natural to quote Traité desd Ordres at the beggining of an essay on trifunctional model. We would be more surprised to find the following proposition :
There is only "three roads for young men, one of the priest, one of the peasant, one of the fighter... The religious estate, because he already have, in a more important degree and more pure, the sum of fighter's virtue...The work of the land because, putting man in permanent contact with nature and his creator, teaching him virtues of endurance, patience and perseverance in effort, that lead him naturally to necessary heroism in battlefield"
Three "estates" (the word is there), three functions (the same : to serve God, preserve the State by arms, take from soil food) and being hierarchised as such. The formulation isn't the same that said. A precision - the ons that Loyseau call "the ones and the others" are there defined as "men" as in : male adults, feminine not being included by such organisation - and two differences. No "orders" there, but "roads", ways, and that are chosen, vocations - while these constitue gradations, as the same individual could, should succesivly engage in third way, then the other, eventually the first and, assuming in his llife all three mandates, "rise up" progressivly from earth to heaven, from "nature" to his "creator". Gradations are then of a perfection, of a progressive "purification".
A scale of virtures : this speech is less political than moral; what it proposes in reality, it's ascetism. On the other hand these three "roads" aren't the only ones. They are only the good ones. Of the other, this manichean speech, doesn't say a word. Because it condamns them.
All of part of society is then cursed, rejected, denied. It proclaims that the only ones that doesn't deviates are answering to the call of God : priest, fighter, peasant.
You would argue that it's the proposition of Loyseau, at the end of Middle Ages rather than XIth. While Duby notices that it's in the continuity of Aldébaron and Gérard, granted.
But first some reflections.
What do we have there?
- A social division that is not rigidified, but mobile. We have enough medieval exemple of people going from an estate to another to support that.
- A social division where women doesn't fully belong. They do transmit a social link but far less than in previous times (The most obvious legacy would be the transmission of free or servile characteristic to its children rather than trough the husband).
An important part of the caste system is the more or less important endogamy. You can have a real endogamy when women aren't really considered part of a social group to begin with.
- A text written down by a cleric, pointing out that the most perfect role is the religious function? I'm truly shocked by the revelation. Remember that all these texts were written by people that had not only all the interest to put their functions at pinnacle, but were ideologically prone to genuinly consider as such.
At some point, you may wonder if it was really a social treaty, or more of a wishful thinking.
- Of course, the most obvious, the social mobility through the trifunctionality, that existed as well in Gallic society (Druids being from differents social orders before reaching their functon).
I would use that by pointing that, nowhere, Duby said the trifunctional model is only Gallic and foreign to Rome : the author mentions regularly Dumézil (up to the "trifunctional model" that is a dumezilian formulation) and does'nt go against the main point of Dumézil that is about an Indo-European social division.
So let's see other texts, some being mentioned in the very same book you quote.
Providence institued diverse gradations and distinct orders as for minors show deference to powerful, and if powerful give love minors, is realised true concorde and conjonction from diversity. The universal communauty couldn't indeed subsiste in any way if the global order of disparity didn't preserved it.
That creation wouldn't be ruled in egality, is taught for us by the exemple of celestial militias : there's angels, there's archangels, that, obviously, aren't equals, ones being diferrent from the others in power and order.
There, nothing about the absence and impossiblity to change, but about an augustinian conception of the world's ordering. There's groups and functions that are established from all eternity, and the world should reflect that to be in cunjunction with God.
Now, let's see Adalbéron's poem directly. You'll excuse me to not translate it entierly, it's a relativly long text.
First, what does the bishop say? That the orders aren't respected.
Public now today this tewts transcripted by famed Crotoniates, where is this epigraph : Lex Antiquissima, and that give this important precepct : "Good will resist you? Use violence!".
That all in the ecclesiastical order be transformed at the will of absolute power : it's this lazy rustre, ulgy and covered by shame, that is to be crowned with a magnificent mitre with a thousand of jewel. As for bishops, these keepers of traditions, they're forced to clothe themselves with habit : let them do oraisons, bow, observe monastic silence, and lower humbly their head; let them go, these robbed ministers, follow without end the plough, prickle at hand, singing hymns of exile of our first father.
A prelate place is empty? Quick : let's consacrate it a shepherd, a sailor, the first come, why bother? Be careful, that said, and scrupulously watch this point : that none of them that is taught Holy Scriptures, and that no one of his days were consacred to study : counting on its fingers alphabet's letters is enough.
There's the first of the Church, the masters that world must defer before : order is gaven to great kings themselves to not do without them
When you begin a treaty about social order, by saying social order isn't respected in first place, you have to wonder how much the following isn't wishful thinking.
I won't translate all this passage, but roughly : he complains that monks go to battle, have spouses, etc. Basically that orders aren't cloistered.
It gets better, as the whole text must be understood as part of a fight against Clunisian order. You probably remember the passage with the man sent to Cluny as monk, and coming back as a soldier, swaring by Jupiter and Mars, despising the bishop and social order?
What's even funnier is that Cluny was what was dynamic then, supported by southern and northern nobility in search of spiritual needs.
Even in religious function, Adalbéron wasn't followed. At this point the credibily of the text as a dominant treaty of social order is really duvbious. (It doesn't help the whole poem is a discussion with Robert II that is hostile, if not more, to Adalbéron's ideas).
Let's take a look at how he descibes the orders.
One [of the rules Church must abide] is the divine law : it doesn't make any distinction in the attribution of his ministers ; it makes of all equals of condition, while dissimilar on how birth or rank made them; for it the son of a worker isn't inferior to a king's heir
Even inside orders, the social stratification along Adalbéron isn't really rigid.
Nowhere in the text is made an allusion on how all of that is inherited, or should be inherited automatically. The main accusation is about people unworthy of religious charges (again, it have to be understood as a problem with religious changes in XI, and not a genuine attempt to describe society) still have them.
So, I'm sorry, but I honestly don't see if you read both Duby's book and Adalbéron's poem how you can consider even a theoritical "quasi-caste" system in the XIth century.
Not that the text, and others, didn't were used later by a far more powerful royalty to promote its own views (organising society along fully hierarchical, while not endogamic/cloistered) is a thing. But that's happen in the XIIIth century, and the conceptions more used as a, to quote Duby, "ideal" than actual social reality.
While romanization had erased the 'trifunctional' division of the society -priesthood being in Rome just a step in the political career, and citizenship & military service being the 2 sides of the same coin- christianization (emergence of a sacertodal class isolated by taboos on meat, on sex...) and the invasions (creating a warrior aristocracy) potentially reintroduced it.
Trifunctionality is present in classical Rome (I won't go into pre-classical Rome, that Dumézil analysed)
The equivalence, up to Caracalla, between citizen and soldier (citizenship being mandatory to have a right to rule or at least acceed honors or being considered honestior) point out that. The warrior function was the marker of the freeman, as in germanic or greek society (while, of course, in a different manner)
As for piresthood, I wholly disagree it was only a career path.
Look at the flamines taboos that are quite similar to other IE (or IE-zed) priesthood : not carrying weapons, special clothes, food taboos, and that's only for the "regular" flamine. Higher you get, more taboos there were.
It only gave up sacerdotal function with the rise of christianism, putting flamines into a strictly civilian role.
The isolation of priesthood on taboos is far earlier than christianism, and dare I say, Christian sacerdotal class taboos were far less important than their predecessors, being open to all social classes being an important factor there.
There was a 4th category of those living 'outside the society' (the Jews & later the Roms, the various 'outlaws': escaped serfs, marauding deserters...) of 'untouchable'.
Not the case : conversions, or even geographical displacement allowed them to enter fully in medieval society.
And the characterisation of Jews, Heretical and such as wholly distinct and outside the society dates, roughly, from Lateran Council in 1215. Before that (while declining), the presence of Jews along Christian (and even inside Christian) society is well attested (as in the absence of cloistered Jewish neighbourhoods before the XIIth century in the north of Europe, later for the south).
The only real "untouchable" groups in Europe are Lepers or groups tought as descendents of Lepers and inheriting their disease (as Cagots). These groups weren't defined religiously or ethnically, but by an inner impurity (making them closer to pariah that groups you mention ever were).