Which Christian ideas, if any, helped bring us into the modern world?
I think John Adams points us in the right direction with the following:
Defence of the Constitutions of Government
of the United States of America
(Source, Charles F. Adams, ed., The Works of John Adams  Vol. 6, p. 3-4)
There have been three periods in the history of England, in which the principles of government have been anxiously studied, and very valuable productions published, which, at this day, if they are not wholly forgotten in their native country, are perhaps more frequently read abroad than at home.
The first of these periods was that of the Reformation, as early as the writings of Machiavel himself, who is called the great restorer of the true politics. The "Shorte Treatise of Politick Power, and of the True Obedience which Subjects owe to Kyngs and other Civile Governors, with an Exhortation to all True Natural Englishemen, compyled by John Poynet, D. D.," was printed in 1556, and contains all the essential principles of liberty, which were afterwards dilated on by Sidney and Locke. This writer is clearly for a mixed government, in three equiponderant branches, as appears by these words:
"In some countreyes they were content to be governed and have the laws executed by one king or judge; in some places by many of the best sorte; in some places by the people of the lowest sorte; and in some places also by the king, nobilitie, and the people, all together. And these diverse kyndes of states, or policies, had their distincte names; as where one ruled, a monarchie; where many of the best, aristocratie; and where the multitude, democratie ; and where all together, that is a king, the nobilitie, and commons, a mixte state; and which men by long continuance have judged to be the best sort of all. For where that mixte state was exercised, there did the commonwealths longest continue."The second period was the Interregnum, and indeed the whole interval between 1640 and 1660. In the course of those twenty years, not only Ponnet and others were reprinted, but Harrington, Milton, the Vindiciae contra Tyrannos, and a multitude of others, came upon the stage.The third period was the Revolution in 1688, which produced Sidney, Locke, Hoadley, Trenchard, Gordon, Plato Redivivus, who is also clear for three equipollent branches in the mixture, and others without number. The discourses of Sidney were indeed written before, but the same causes produced his writings as did the Revolution.
Americans should make collections of all these speculations, to be preserved as the most precious relics of antiquity, both for curiosity and use.
This seems to be part of the thread of political theology that heavily influenced the founding. I also think it is interesting that one the three periods he references is the Revolution of 1688 that Brad Hart posted on the other day. I think the name of the book was, "The First Modern Revolution". Maybe Christian political theology did help usher us into the modern world. That is the thesis of Gary Amos in his book, "Defending the Declaration: How the Bible and Christianity influenced the writing of the Declaration of Independence".
He gives some compelling evidence that the founders laid out the same legal case for independence that many cited here by Adams had used before. Maybe our founding was not as "revolutionary" as some would give it credit for. Could it have been tied to a long tradition of ideas that could be traced back to pre-Aquinas Christianity? We shall see.
More to come...