>>18
That's only for the CL package.
Usually you never alter the CL package(altough, many implementations let you), you make your own package and you're free to have any symbols you want named whatever you want them. Most commonly you use the COMMON-LISP package, but if you want, you can always shadow those symbols, or not import CL at all (if you need to use stuff from CL, just use the full symbol name, which includes the package name). So
>>17 would be right if he said, "shadow" or "don't import them in the first place". You can also shadow them in CL-USER, which is the default package nickname for COMMON-LISP-USER, which is the default value of *package*. CL-USER typically uses CL and a bunch of common implementation-specific packages.