Here’s my take on this whole Scheme-vs-Common-Lisp issue. Common Lisp’s sole purpose is providing a practical environment in which to program real-world applications. In this regard, though, it doesn’t offer anything that younger systems like Python or Ruby don’t. Therefore, there’s just no reason to learn Common Lisp nowadays. Scheme, on the other hand, has a completely different purpose, for which it is well suited: teaching. There’s no serious alternative to Scheme in teaching basic principles of computer science. Scheme thus still has a reason to exist, while Common Lisp does not.