in response to Robin's "what it means to 'speak Chinese'"
It's actually a bit weirder and more complicated than that. As the
article points out (and as I learned when I studied Mandarin about,
oh, 20 years ago), the _semantics_ of the written Chinese characters
are basically the same in all Chinese dialects, but the spoken
syllables differ radically. It's as if anyone that could read
English could also read, say, Italian, and vice versa...without
conferring any ability to speak or understand the other language.
This is further complicated by the fact that mainland Chinese
generally (I think) uses simplified versions of the "original"
characters, whereas Taiwanese use the original characters, but that's
not really an issue in mainland China, AFAIK. (I might possibly have
it backwards, but the difference is there regardless.)
(Incidentally, I believe that Japanese characters (not the
"alphabetic" ones) also share at least some of the semantics with
written Chinese, putting Japanese, in a sense, on a similar footing
with the various Chinese dialects.)
On a random cultural note, I believe that this linguistic oddity may
explain why it is that I have heard that some Chinese, when speaking
Chinese to other Chinese, will sometimes scribble some of the
characters on their palms with their fingers: it disambiguates.