> if you didn't have the import from Base, what can you not do?

So the part that gets loaded when you load the language/compiler is what is referred to as Base. So, it's kind of impossible to not have it and it is part of the language. So it's somewhat like asking, what can you do without "importing" integers? (ok, that's a hyperbole, but you get the idea ;) ) But, the source code does get shipped, so you might actually go in there and change stuff if you want, and Julia will pick up those changes - even, to get back to that hyperbole, how integers are defined, since they're implemented in pure Julia. I'm not a 100% sure what you're aiming at, but does that answer your question? ;)