What's that cloud enveloping America, pessimism or realism? In this hour of To the Best of Our Knowledge, America's obsession with the idea of decline. A new theory of history predicts another Great Depression just around the bend. Also, government and alien conspiracies on The X-Files. The truth is out there.

SEGMENT 1

Historian Neil Howe tells Steve Paulson about his theory that history moves in generation-long cycles and that the pattern of these cycles repeats constantly. He says we're just about ready for a massive change. Howe is co-author (with William Strauss) of "The Fourth Turning."

SEGMENT 2:

Arthur Herman teaches history at George Mason University. His book is "The Idea of Decline." Herman tells Judith Strasser about the tradition of cultural pessimism and what makes today's doomsayers different. Also, pessimism and paranoia are the hallmarks of The X-Files, and viewers can't get enough. Mary Kaye Schilling, senior TV editor at Entertainment Weekly and die-hard fan, talks with Jim Fleming about the show, it's cultural assumptions and it's popular appeal. Remember, the truth is out there.

SEGMENT 3:

Jared Diamond is an evolutionary biologist at UCLA. His new book is "Guns, Germs, and Steel: The Fates of Human Societies." Diamond tells Steve Paulson that accidents of nature have done more to shape human destiny that any culture's imperial ambitions.

Distribution dates:

• week of 04/20/97 - hour 3
• week of 05/03/98 - hour 3