This book reflects a trend that troubles me: the publishing of a group of loosely connected papers by different authors as a book. Journals, not books, seem to me to be the place for such papers. Journals provide a format for ongoing discussion through letters or later the publication of related papers. There is no such dialogue in a book of separate papers, and one is left with a lack of coherence. Such a book has no organized thesis or point of view.

Publishing a series of journal articles as a book seems to have been spurred on by the current tendency to publish all addresses, lectures, and symposia that have been delivered. The form, structure, and content of a "spoken" paper is necessarily different from