How the Scots Created the Modern World

I'm reading Arthur Herman's recent wildly popular book, How the Scots Created the Modern World, and I am, overall enjoying it greatly.  And I should probably finish it before I begin commenting on it.  Except...

It feels very much as if he come to a conclusion--that much of the intellectual foundation for modernity (however one may choose to define it, but let's go with representative, non-authoritarian governments and private-property ownership economies, with a strong commitment to the rule of law) arose in Scotland.  And that the book was written as, well as more than an argument for that conclusion.  More as a campaign speech.  Two examples, one fairly minor, the other, to me, extremely serious.

Minor.  The Scots thinkers about whom he writes clearly did not agree with each other.  Hume's skeptical rationalism and Witherspoon's religious-based appeals to custom and order make strange bedfellows.  Adam Smith's foundation of the wealth of nations in the operation of reasonably free markets does not play well with James Steuart's mercantilism (his Principles of Political Economy was published in 1767, 9 years before Smith's An Inquiry Into the Nature and Causes of the Wealth of Nations--they were, essentially, contemporaries).  This is, however, somewhat minor.  No period of intellectual ferment--and the late 18th century was that--is a single stream of thought.

Major.  Herman devotes a chapter to the role of Scots who emigrated either from Ulster or from Scotland to America in the foundation of the United States.  He notes their championing of limited government and individual rights.  He also notes that many of them were prominent politically and professionally in the southern colonies.  Oddly, to my mind, there are only two mentions in that chapter of slavery.  One is a reference by one of the people he focuses on, referring to England's restrictions on colonial economic activity as slavery.  The other is a throwaway mention of disputes over slavery during the (1787) Constitutional Convention. 

But is seems obvious to me (as, indeed, it did to a fair number of people in the late 18th century) that in a society as dependent as the U.S., and in particular as dependent as the southern colonies-soon-to-become-states, were on slavery, rhetoric about freedom may ring hollow.  This disconnect between what people like Patrick Henry were saying in the course of their political disputes with England and how they prospered--by owning, and exploiting, slaves--is too stark not to at least address. 

So I don't know where I will come down at the end.  At the moment, there is a serious flaw at the core of the argument, and one that I'm not sure is capable of being remedied.