现在，看起来似乎数学和物理的世界已经拥有足够多种类的数了。虽然还存在本书没有提到的数的类型，但是自20世纪上半叶以来，我们还不需要对数学和科学中常用的数进行大的改造。
本书中我们对数学进行了一次“热气球观光之旅”，伴随着以上的观察结果，我们也到该说再见的时候了。我们从地面出发，渐渐升到了空中，我希望从这个高度上，丰富多彩又神秘莫测的数的世界能够吸引读者朋友的注目。
[1]　数学中抽象代数的一支。
英文原文
Peter M. Higgins
Numbers
A Very Short Introduction
Preface
The purpose of this little book is to explain, in language that will be familiar to everyone, what are the various kinds of numbers that arise and howtheybehave. Numbers allow comparisons between all manner of things, and anyone with no understanding of numbers would be lost in the modern world where things numerical are there to greet us at every turn. We should realize however that, despite their familiarity, numbers have no physical existence but rather are abstractions that we elicit from the world we find ourselves in. To develop a clear picture of how they operate, it is sometimes better to consider them in their own right,without reference to anything else.