How can we draw a line and conclude a century? we may celebrate as the hands of the clock reach midnight and hang a fresh calendar, but it is not that easy to discern the beginnings or ends of deep-seated processes of historical change. In the Introduction to this book, we noted that our goal was to write a thematic history of the twentieth century that focused on significant human experiences. Such experiences hardly begin and end at the turn of centuries, or if they do it is coincidental.