"APL has been compared to a diamond, which cannot be made into a larger diamond by the addition of a second one. LISP, in this context, is a ball of clay."

I couldn't have said it better myself. I've come to think that APL and Lisp represents two diametrically opposing philosophies about structuring programs. Right now I'm leaning toward the opinion that the ball of clay approach has run its course and is no longer (or maybe never way) viable. The thousands of layers of abstraction is no longer viable, for both performance and productivity reasons.