David Horowitz has been a bellwether of true-believer political activism for roughly four decades. He spent much of the '60s and nearly half of the '70s as a New Left activist, editor of Ramparts magazine, and a fellow traveler with the Black Panthers. After his friend Betty Van Patter clashed with a Panthers leader, disappeared, and then reappeared as a severely beaten corpse, Horowitz went through a political conversion.

Horowitz has become one of the most visible conservative activists of the Baby Boom generation. He oversees a pugnacious website, www.frontpagemag.com, and a flow chart of left-wing mischief called www.discoverthenetworks.org.

One aspect of Horowitz's life remains largely unchanged by his second thoughts: his decades-long agnosticism. As Horowitz expresses it these days, that agnosticism will fit any unbelieving baby boomer like a well-worn pair of jeans.

In The End of Time, Horowitz reflects on his brush with death that began in September 2001. Three days after the attacks on the World Trade Center, Horowitz learned that he had prostate cancer. He devotes one concise chapter to his battle with the disease, but the knowledge of his mortality haunts the entire book. When Horowitz read from his book at one of those charmingly obscure events covered by C-SPAN's Book TV, he seemed less a militant culture warrior and more a man who knew that any day he might no longer see his beautiful second wife, April.

It's clear that April believes in God, but the rest of her beliefs sound about as coherent as a treacly e-mail involving puppies, terminally ill children, and guardian angels. In the book, April pleads with her husband to be less arrogant toward God, because, "If you don't believe, you won't be there [in heaven] ...