The essays composing this book were written at different times for different occasions. Yet I venture to believe that, put together in a single volume, they will present a mental unity-a single body of interests, observations, and ideas, which is one individual's reaction to the spectacle of the universe. In the history of mankind, during these last few thousand years, in which mankind has begun to have what may be called in the more special sense a history, the two predominant factors appear to be, (1) the rise of rationalist culture, first in the ancient Greek world and then again in modern European civilization, and (2) the entrance of the Christian life into the world process.