THIS BOOK IS A LONG-DELAYED PRODUCT of a series of lectures
that I gave in June, 1956 at a conference at Wabash College
directed by John Van Sickle and Benjamin Rogge and spon-
sored by the Volker Foundation. In subsequent years, I have
given similar lectures at Volker conferences directed by Arthur
Kemp, at Claremont College, directed by Clarence Philbrook,
at the University of North Carolina, and directed by Richard
Leftwich, at Oklahoma State University. In each case I covered
the contents of the first two chapters of this book, dealing with
principles, and then applied the principles to a varied set of
special problems.

I am indebted to the directors of these conferences not only
for inviting me to give the lectures, but even more for their
criticisms and comments on them and for friendly pressure to
write them up in tentative form, and to Richard Cornuelle,
Kenneth Templeton, and Ivan Bierly of the Volker Foundation
who were responsible for arranging the conferences. I am
indebted also to the participants who, by their incisive probing
and deep interest in the issues, and unquenchable intellectual
enthusiasm, forced me to rethink many points and to correct
many errors. This series of conferences stands out as among
the most stimulating intellectual experiences of my life. Need-
less to say, there is probably not one of the directors of the con-
ferences or participants in them who agrees with everything
in this book. But I trust they will not be unwilling to assume
some of the responsibility for it.

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