The question was what causes societies to move towards being more voluntary. You may think that eternal vigilence caused it but that doesn't change the fact that it seemed to emerge in the 1600s and that it wasn't there in the 1500s.I'm going to stick with "No-one knows."
That's not at all true. Go back and read this thread, there are definable examples to at least 1291 (the foundation of the old Swiss Confederacy,
https://en.wikipedia.org/wiki/Old_Swiss_Confederacy#Foundation) and some credible, yet undocumentable, examples of same that go back much farther. Do you contest that the Swiss Confederacy was founded upon ideals that would be consistant with a modern sentiment of a "voluntary" society? Bear in mind, that the foundation 'myth' (can't be supported with any historical documents) of the old Swiss Confederacy is the story of William Tell (
http://en.wikipedia.org/wiki/The_Apple_and_the_Arrow) leading an uprising against a tyranical & absolute monarch, and that the 'Founding Fathers' of the United States appealed to the Swiss for financial support during the Revolutionary War because they believed they would find ideological like minds.
They did, and some rather wealthy ones as well.
EDIT: That particular book is part of my kids' homeschooling curriculum, for
kindergarten.