I've always found it unfortunate how many people joke about this quote while at the same time praising folks such as Nassim Taleb. I think it's fair to say that

I've always found it unfortunate how many people joke about this quote while at the same time praising folks such as Nassim Taleb. I think it's fair to say that a Black Swan is analogous to an unknown unknown. I'm no fan of Rumsfeld, but the idea itself seems valid to me.