Meaningful Statements...?

     So today, I was looking through and came across Boondocks. Y'all know that black comedy cartoon with two boys who move with their grandfather to the suburbs? The one that addresses life events in a comic satirical manner?
     Well, in Season 1, Episode 5, Ed Wuncler's friend makes this statement:  

                "The absence of evidence, is not the evidence of absence."

           I'm still trying to decipher that. Any help?