"Good work speaks for itself."

Except when it doesn't.

Joshua Bell playing his Stradivarius in Grand Central Station - nary a viewer.

Michael ONeil's photographs of random mundane items: broken watch, wallet, keychain. Boring until we are told they were artifacts found in the rubble of the World Trade Center.

Boring portraits of men in front of a white background... until we learn they are all on death row.

Maybe we don't have to "explain" but context is certainly part of the art itself.