Michael Shermer, the founder and editor of Skeptic magazine, has never received so many angry letters as when he wrote a column for Scientific American debunking 9/11 conspiracy theories. Mr. Shermer found himself vilified, often in CAPITAL LETTERS, as a patsy of the sinister Zionist cabal that deliberately destroyed the twin towers and blew a hole in the Pentagon while secretly killing off the passengers of the flights that disappeared, just to make the thing look more plausible.

He tells this story in his fascinating new...