This book is a product of love and respect. If that sounds rather odd I
initially apologise, but let me explain why I use those words. The
original manuscript was of course Freudenthal's, but his colleagues have
carried the project through to its conclusion with love for the man, and
his ideas, and with a respect developed over years of communal effort.
Their invitation to me to write this Preface e- bles me to pay my
respects to the great man, although I am probably incurring his wrath
for writing a Preface for his book without his permission! I just hope
he understands the feelings of all colleagues engaged in this particular
project. Hans Freudenthal died on October 13th, 1990 when this book
project was well in hand. In fact he wrote to me in April 1988, saying
"I am thinking about a new book. I have got the sub-title (China
Lectures) though I still lack a title". I was astonished. He had retired
in 1975, but of course he kept working. Then in 1985 we had been helping
him celebrate his 80th birthday, and although I said in an Editorial
Statement in Educational Studies in Mathematics (ESM) at the time "we
look forward to him enjoying many more years of non-retirement" I did
not expect to see another lengthy manuscript.