In 1924 the firm of Julius Springer published the first volume of
Methods of Mathematical Physics by Richard Courant and David Hilbert. In
the preface, Courant says this: Since the seventeenth century, physical
intuition has served as a vital source for mathematical problems and
methods. Recent trends and fashions have, however, weakened the
connection between mathematics and physics; mathematicians, turning away
from the roots of mathematics in intuition, have concentrated on
refinement and emphasized the postulational side of mathematics, and at
times have overlooked the unity of their science with physics and other
fields. In many cases, physicists have ceased to appreciate the
attitudes of mathematicians. This rift is unquestionably a serious
threat to science as a whole; the broad stream of scientific development
may split into smaller and smaller rivulets and dry out. It seems
therefore important to direct our efforts toward reuniting divergent
trends by clarifying the common features and interconnections of many
distinct and diverse scientific facts. Only thus can the student attain
some mastery of the material and the basis be prepared for further
organic development of research. The present work is designed to serve
this purpose for the field of mathe- matical physics . . . .
Completeness is not attempted, but it is hoped that access to a rich and
important field will be facilitated by the book. When I was a student,
the book of Courant and Hilbert was my bible.