This book grew out of my interest in what is common to three
disciplines: mathematics, philosophy, and history. The origins of
Zermelo's Axiom of Choice, as well as the controversy that it
engendered, certainly lie in that intersection. Since the time of
Aristotle, mathematics has been concerned alternately with its
assumptions and with the objects, such as number and space, about which
those assumptions were made. In the historical context of Zermelo's
Axiom, I have explored both the vagaries and the fertility of this
alternating concern. Though Zermelo's research has provided the focus
for this book, much of it is devoted to the problems from which his work
originated and to the later developments which, directly or indirectly,
he inspired. A few remarks about format are in order. In this book a
publication is indicated by a date after a name; so Hilbert 1926, 178
refers to page 178 of an article written by Hilbert, published in 1926,
and listed in the bibliography.