In reading about the Civil War and about Scotch-Irish history, I have encountered the "Celtic South" theory a few times. If you're not familiar with it, the idea is that Southerners were largely descended from Celtic people, Northerners from Anglo-Saxons from southern England. It connects Southern culture to Celtic roots and portrays the war as a clash of these different age-old cultures.
I believe it originated with Grady McWhiney and his book "Cracker Culture":
http://www.nytimes.com/2006/04/30/us/30mcwhiney.html?_r=0
Other people have written about it too, though -- Jim Webb leaned pretty heavily on the idea in "Born Fighting."
I was wondering what you here and historians in general think of it, if you give it any credence or if it's just a bunch of malarkey. We all know large numbers of Scotch-Irish people settled in the South and had an influence on the culture. But the idea that they were the predominant influence, and that they were so vastly and irreconcilably different from their fellow English-speaking Protestants in the northern states that this cultural difference was a main cause of the war, strikes me as highly suspect.
For starters, you could probably debate forever just how "Celtic" Lowland Scots and their descendants in Ulster and America are. Many Scotch-Irish writers of the 19th century went out of their way to argue that their ancestors were Anglo-Saxons, just like the English. Just one of many such examples of this I could cite is on page 187 of this work:
As late as the 1960s, opponents of integration leaned on their Anglo-Saxonness in their rhetoric -- George Wallace and his "Anglo-Saxon Southland" is one famous example, but there are others.
Much of this was doubtless an attempt to fit in in an era where Anglo-Saxons were viewed as superior. Modern genetic research has shown that English people have plenty of Celtic ancestors anyway. Distant genetics aside, though, most of the Scots who settled in Ulster and later came to America were English-speakers (or Scots if you consider it a separate language), and had been for generations. To portray them as completely different from the English seems about as extreme, and wrong, as the opposite argument that they were just like the English.
Plus, the coastal South was settled mostly by the English, as I learned it. And there were plenty of Scottish and Scotch-Irish people who settled in the North -- not as many as in the Appalachians, true, but they were a substantial influence in some areas. (I'm leaving out the Catholic Irish for the purposes of this because they were too new in this country at the time of the war to have had much influence on its causes.) Plus, advocates of this theory count as "Celtic" many people who have been speaking English for hundreds of years before coming to America. I doubt your average northern Englishman in 1700 would have regarded himself as having much in common with a Gaelic-speaking Scottish Highlander just because he might have had some Cumbric-speaking ancestors in the 11th century.
The whole theory strikes me as an attempt to justify the Southern side of the war by painting it as a romantic fight by Scottish and Irish folks fighting the same battles against those oppressive Yankees that their forefathers fought against the English. Sounds a lot nicer than saying we were fighting to preserve the right to own slaves, doesn't it? But I would be interested to hear what other knowledgable people such as yourselves think of it.
I would agree with your assessment, and would add a couple of criticisms:
As Rowland Berthoff pointed out in his critical review of the McDonald-McWhiney thesis, the distinction between "Celtic" and "Anglo-Saxon" Britain in the 17th and 18th centuries was a lot more hazy than they suggest, and it's definitely a case of overreach to label certain migrants to America as "Celtic" - for example, many of them were Lowland Scots whose culture was closer to that of England than to the Celtic fringe. Nor does the assumption that Celtic regions were pastoralist - in contrast to the plow-driven Anglo-Saxon agriculture - bear closer examination. I strongly recommend that you look at the Berthoff critique for the details.
There's also a problem with assuming that "Celtic" culture has some essential, unchanging core, when in point of fact it was largely the invention of 19th century writers, as Rodger Cunningham has pointed out in this review. David Hackett Fischer made similar claims in relation to "backcountry" culture in Albion's Seed, and was criticized by many for this essentialist approach to culture.
I think you're on to something when it comes to how the "Celtic South" thesis relates to contemporary Southern nationalism. In his book on Confederate re-enactors, Confederates in the Attic, journalist Tony Horwitz provides this gloss on McWhiney's conclusion that "Southerners lost the War because they were too Celtic and their opponents were too English":
Viewed through this prism, the War of Northern Aggression had little to do with slavery. Rather, it was a culture war in which Yankees had imposed their imperialist and capitalistic will on the agrarian South, just as the English had done to the Irish and Scots - and as America did to the Indians and the Mexicans in the name of Manifest Destiny. The North's triumph, in turn, condemned the nation to centralized industrial society and all the ills that came with it. (p. 69)
It is true that the north and the south had different cultures and that honor culture was a big part of the difference. Southerners had a murder rate that was estimated to be as high as 4 times that of the North with less prosecution, because a communal acceptance of honor killings and dueling existed long after such tolerance for violence had abated in the North. You can see that in play during the caning of Charles Sumner by Preston Brooks. Southerners didn't just send Brooks canes to celebrate his defense of slavery, they also related to the idea that Sumner's condemnation of Brooks' relative constituted a besmirching of Brooks' honor and that a violent, one-sided attack was the way an aggrieved superior could reclaim his honor from a lowly attacker.
Of course, the real difference between the two cultures was slavery, pure and simple, and this strange 'celtic' thesis is a way to elide slavery, by producing anything besides slavery which we can make the rationale behind the civil war. Many people, in fact, have argued that the honor culture and violent propensities of Southerners arise out of slavery, where mastery became an ideal and an ideology which included the use of violence as a part of daily life.
Also, something that kind of breaks this down is that, the North and South were made up of many different types of Europeans. Germans and Irish were arriving in the North in droves in this period, Louisiana and South Carolina had numerous French people and of course people of Spanish ancestry were present throughout Texas and Louisiana. Besides, the most Scots-Irish part of the South, Appalachia, was the most lukewarm area toward secession of any part of Dixie, which is a big reason West Virginia is a thing these days. Similarly, Appalachian parts of Kentucky, virginia, west virginia, and tennessee saw bloody fighting between local individuals with conflicting loyalties to the respective sides....