I think of art, at its most significant, as a DEW line, a Distant Early Warning system that can always be relied on to tell the old culture what is beginning to happen to it.

This quote suggests that art is an important indicator of what is happening in society. It’s like an alarm system (DEW line) that warns people of changes that are occurring. The old culture is able to rely on art to give them a heads up to what is coming, so they can adjust accordingly.