Age of Enlightenment
The Enlightenment was an intellectual movement which advocated rationality as a means to establishing an authoritative system of aesthetics, ethics, and logic. It overturned the notions of mysticism and faith in individual revelation as the primary source of knowledge and wisdom
The Enlightenment inspired the framework for the American and French Revolutions (among others); the democratic government of the United States is largely an enlightenment innovation.
The liberal ideology, which emphasizes personal liberty (immunity from the arbitrary exercise of authority), arose from Enlightenment ideas.
David Brin seems to view The Enlightenment as synonymous (or nearly so) with the move away from feudalism as a popular form of government in the past two centuries or so, among other things. (Also "Modernity", rationality. More notes later, now that there's a page for this. --Woozle 15:53, 30 July 2006 (EDT))