Never before in the history of mathematics has there been an individual
theorem whose proof has required 10,000 journal pages of closely
reasoned argument. Who could read such a proof, let alone communicate it
to others? But the classification of all finite simple groups is such a
theorem-its complete proof, developed over a 30-year period by about 100
group theorists, is the union of some 500 journal articles covering
approximately 10,000 printed pages. How then is one who has lived
through it all to convey the richness and variety of this monumental
achievement? Yet such an attempt must be made, for without the existence
of a coherent exposition of the total proof, there is a very real danger
that it will gradually become lost to the living world of mathematics,
buried within the dusty pages of forgotten journals. For it is almost
impossible for the uninitiated to find the way through the tangled proof
without an experienced guide; even the 500 papers themselves require
careful selection from among some 2,000 articles on simple group theory,
which together include often attractive byways, but which serve only to
delay the journey.