I approach the reader like St. Denis, with my head in my hands. I know that no specialist would write a book that ranges from Moses and Homer to Erasmus and Machiavelli. Yet, as Preserved Smith has said: "The need is now, surely, for a return to synoptic writing. Here is a map of a large region, not a geological chart of a square mile or a plan of a single city." As on a general map one looks in vain for some special river or road, so here, as I know, omissions will occur to every reader. But no two writers will agree on whom and what to omit; any discussion of so vast and complex a subject must necessarily involve many lacunae. Perhaps a better name for this book might be "Selected Topics in the History of Mediaeval Thought." A discussion of this sort tends to dwell on the achievements of exceptional individuals. The broad stream of mediaeval cultural life flowed in muddier and slower currents. For the earlier Middle Ages, it would be impossible to write a history of the ideas of the masses because of the lack of adequate sources; for the later Middle Ages there are an insufficient number of monographic studies on which to base an adequate general account. So I have confined this book to the history of the interests of the intellectual classes.
The account is inevitably very succinct; every section of every chapter could be expanded into a book. Oversimplification has been unavoidable, and in trying to follow main currents, minor influences had to be sacrificed. Also, in view of the scale on which the book is written, brief dogmatic formulations must often be substituted for full discussions. Most of the subjects herein discussed are so interrelated that they should, at least in any given century, be treated together. This survey often divides things that ought to be united, but the au-