Book excerpt: Raymond Smullyan presents a bombshell puzzle so startling that it seems incredible that there could be any solution at all! But there is indeed a solution — moreover, one that requires a chain of lesser puzzles to be solved first. The reader is thus taken on a journey through a maze of subsidiary problems that has all the earmarks of an entertaining detective story.This book leads the unwary reader into deep logical waters through seductively entertaining logic puzzles. One example is Boolean algebra with such weird looking equations as 1+1=0 — a subject which today plays a vital role, not only in mathematical systems, but also in computer science and artificial intelligence.