'Nihilism' is in the news. What's behind this 'nothing' philosophy?

The damaged front of the American Reproductive Centers fertility clinic stands following a bomb blast on May 17 in Palm Springs, California. A suspected bomber is believed to have post a manifesto to social media before the explosion.

The weekend bombing of a Palm Springs, Calif., fertility clinic has cast a fresh spotlight on a 19th century philosophy linked to Russian revolutionaries. What does "nihilism" mean?

(Image credit: David McNew)