What makes Lisp...Lisp?

If you starting removing features from Lisp, at what point is it no longer Lisp? Some people claim Clojure shouldn't be considered a Lisp. Is it because too much Lisp was removed?

What is at the very heart of Lisp that makes it Lisp?

>>29
Wrong. Do you realize why? first of all, this works only with one type; secondly, you can't use the macro twice; thirdly, even if the macro seems to do some actual work, it doesn't, simply because you have to enter the type name anyway inside the body of the function (to access data).

Tl;dr it's nearly impossible to write a general mapcar in C.

>>32
It's more generic in this sense: (mapcar #'- '(1 2 3)) works to produce (-1 -2 -3); (mapcar (lambda (x) (cons (cdr x) (car x)) '((a . b))) works to produce ((b . a)). In C, you'd have to use two different specialized mapcars, one for integers, one for cons cells; it's impossible to use one function for both tasks.