Scots and English: another view

Is Scots readily understandable by and English person and vice versa in the 17th century or not? I assume M. Pittock overstates the case. But constructing a narrative such as our textbook is a difficult architecture on shifting sands.

Pittock, Murray G. H. Inventing and Resisting Britain: Cultural Identities in Britain and Ireland, 1685-1789. New York: St. Martin's Press, 1997, p. 45: “It would perhaps be not too far off the mark to suggest that about a quarter of the Scottish population spoke Gaelic in 1700 (the vast bulk of the rest speaking Scots, a tongue (now attenuated almost to extinction) as separate from English as Dutch is from German). Wales and Ireland were very heavily Celtic-speaking at the same date.”

Scotland and a Greater England?

Arthur Herman, How the Scots Invented the Modern World: The True Story of How Western Europe's Poorest Nation Created Our World and Everything in It (New York: Three Rivers Press, 2001), 20:

• England and Scotland had been joined together by history and geography since the fall of the Roman Empire.... Both spoke the same language, since the Scottish royal court had adopted English (or a dialect related to Middle English called Scots) back in the eleventh century, relegating Gaelic to the cultural backwater.

We did not, I believe, incorporate this point into our Early Modern England, 1485-1714.