For folks who are confused, an interesting and useful article on why Scheme could be considered a Lisp, why it might not, and why it doesn't really matter. http://wiki.c2.com/?IsSchemeLisp
While it's true folks argue that it doesn't really matter (evidence: the section 'Arguments why it doesn't matter' on that page), I'll counter-argue that they're wrong. Scheme simply isn't the same language as Lisp. That's okay: the entire world doesn't need to standardise on a single language (although if it's going to, Lisp would be preferable to Scheme).
And, honestly, the arguments that it doesn't matter presented on that page are pretty weak. 'It's a pointless distraction' is an assertion, not an argument. Scheme and Lisp are different; they have different philosophies and they solve the same problems in different ways; recognising those differences is recognising the facts; ignoring them is simply ignoring reality. 'The benefits of choice far outweigh the disadvantages of redundant/wasted development work on two incompatible platforms' is clearly, I believe, falsified by the experience of the last couple of decades. When I think of the work which went into Racket (originally a Scheme, but now its own thing) and Clojure, I think of how much better Lisp could have been if that effort had instead been spent on it (and aficionados of either of those languages could say the same thing about effort spent on the other, on Lisp & on other Lisp-like languages).
