This is another thing that is nice about languages with simple syntax (like Lisp and Smalltalk) -- language features and libraries can "look" exactly the same.

This is another thing that is nice about languages with simple syntax (like Lisp and Smalltalk) -- language features and libraries can "look" exactly the same. I think this is one of the big mental barriers to entry for users of other languages. It happens in C++, too, which has an extremely complex syntax. C programmers are used to thinking of operators like + and - as language features because their meaning is defined by the language and can't be changed by programmers. C++ operating overloading continues to be extremely controversial because people who are used to C get angry that + and - can "unexpectedly" have meanings other than the meanings defined in the C language. I know that's a special case, nothing like the general mutability of Lisp syntax, but I just wanted to point out that the differences pro (superior freedom/expressivity) and con (fear of confusion) happen whenever one language is slightly more programmable than another, not when a language has simpler syntax. (Of course, any sane person designing a programmable language would prefer minimal syntax.)