Julian Schwinger had plans to write a textbook on quantum mechanics
since the 1950s when he was teaching the subject at Harvard University
regularly. * t Roger Newton remembers: [A] group of us (Stanley
Deser, Dick Arnowitt, Chuck Zemach, Paul Martin and I forgot who else)
wrote up lecture notes on his Quantum Mechanics course but he never
wanted them published because he "had not yet found the perfect way to
do quantum mechanics. " The only text of those days that got published
eventually - following a sug- gestion by, and with the help of, Robert
Kohler: !: - were the notes to the lectures that Schwinger presented at
Les Houches in 1955. The book was reissued in 1991, with this Special
Preface by Schwinger [3]: The first two chapters of this book are
devoted to Quantum Kine- matics. In 1985 I had the opportunity to review
that development in connection with the celebration of the 100th
anniversary of Hermann Weyl's birthday. [ . . . ] In presenting my
lecture [4] I felt the need to alter only one thing: the notation.
Lest one think this rather triv- ial, recall that the ultimate
abandonment, early in the 19th century, of Newton's method of fluxions
in favor of the Leibnizian calculus, stemmed from the greater
flexibility of the latter's notation.