The axioms of a complex Banach algebra were very happily chosen. They
are simple enough to allow wide ranging fields of application, notably
in harmonic analysis, operator theory and function algebras. At the same
time they are tight enough to allow the development of a rich collection
of results, mainly through the interplay of the elementary parts of the
theories of analytic functions, rings, and Banach spaces. Many of the
theorems are things of great beauty, simple in statement, surprising in
content, and elegant in proof. We believe that some of them deserve to
be known by every mathematician. The aim of this book is to give an
account of the principal methods and results in the theory of Banach
algebras, both commutative and non- commutative. It has been necessary
to apply certain exclusion principles in order to keep our task within
bounds. Certain classes of concrete Banach algebras have a very rich
literature, namely C*-algebras, function algebras, and group algebras.
We have regarded these highly developed theories as falling outside our
scope. We have not entirely avoided them, but have been concerned with
their place in the general theory, and have stopped short of developing
their special properties. For reasons of space and time we have omitted
certain other topics which would quite naturally have been included, in
particular the theories of multipliers and of extensions of Banach
algebras, and the implications for Banach algebras of some of the
standard algebraic conditions on rings.