It's kind of a boring and tired point, but for another perspective on "is X a Lisp?" it's worth reviewing the Lisp 1.5 manual from 1962: http://www.softwarepres

It's kind of a boring and tired point, but for another perspective on "is X a Lisp?" it's worth reviewing the Lisp 1.5 manual from 1962: http://www.softwarepreservation.org/projects/LISP/book/LISP%201.5%20Programmers%20Manual.pdf http://www.softwarepreservation.org/projects/LISP/book/LISP%... Consider the program at the bottom of page 29 that calculates the length of a list. What's the delta to get it to run in X? In Clojure, quite a lot of modification is needed. Scheme, slightly less. Common Lisp though, all you have to do is change the archaic top-level "DEFINE (( (LENGTH ..." to "(defparameter LENGTH...", and "ADD1" to "1+", and to call it change "LENGTH ((A B C D))" to "(LENGTH '(A B C D))", similar for "LENGTH (((X . Y) A CAR (N B) (X Y Z)))". The features of cons cell lists (including the syntax (X . Y)), lambdas, PROG, setq, labeled gotos, and even being able to use SHOUTING names if you want, have all been retained throughout the decades. The program from 48-51 works as an example too. Here's a small driver someone wrote in CL to run it without having to modify it: http://www.informatimago.com/develop/lisp/com/informatimago/small-cl-pgms/wang.html http://www.informatimago.com/develop/lisp/com/informatimago/... One notable feature is that of being able to TRACE a function, which is quite handy, and is retained in modern Lisp systems. You could write such a driver in any language, sure, but it wouldn't be as small and simple in anything but Common Lisp, because so many of the functions in Appendix A have been carried forward through history with many Lisps until Common Lisp, so you can just pass them through to the base Lisp, no need to remap and wrap things/write a small interpreter like you would in Clojure/Scheme. A language that just ignores all of that history and makes no attempt to be backwards compatible with any of it can't be considered a "true Lisp", even if it shares other Lispy features. But again, it's a tired argument, and whether someone disagrees isn't very important. To me, Clojure is a Lisp-inspired language (like so many others, e.g. Julia), and is attractive on its own merits, without having to crib the good name of Lisp.