evidence: Muhammad Ali: In his own words "Who's the greatest? Who's the greatest?" [...] And he said it all with a voice the world came to know and embrace -- as powerful as any punch he ever threw. That voice, that never wavered, as Ali stood for what he believed. [...] Impossible is not a fact. It's an opinion. Impossible is not a declaration. It's a dare. Impossible is potential. Impossible is temporary. Impossible is nothing."