Neal Stephenson: I didn't really have a good grip on this, either, and still don't, but it appears that the Enlightenment refers to a bunch of stuff that was triggered by a lot of thinkers who were active during the late seventeenth century. Work that was done by the Royal Society and other natural philosophers of the time, combined with other currents in politics and religion, led to this later thing called the Enlightenment, more of an eighteenth-century phenomenon. It doesn't really enter in to the book that I'm writing here.