You’re quite right: “can not” can mean the same thing as “cannot”, i.e. “is unable to”. But it’s ambiguous; it can *also *mean “is able to not”. And I’d bet that’s why “cannot” is the far more common spelling.
So when I see “can not”*, I usually assume it’s the second meaning, “is able to not”. I figure that if the person meant “is unable to”, given a choice, they’d use the unambiguous spelling. I’m just kind of surprised that more people don’t make the same assumption.
However, “is unable to” is a far more commonly expressed idea than “is able to not”, so I suppose some folks are just going with what the sentence most likely means, or maybe not even noticing there’s a second possible meaning.
Actually, my personal opinion on conversational usage of that phrase agrees with yours too, Heart of Dorkness, but rules of civilized debate and all…we got out-cited. Granted I didn’t look too hard, but the only cites I found for “can not” being able to be used that way were a bunch of grammarian blogs and writing-class FAQ sites, which aren’t the most authoritative things out there.
I answered S and Q are the same because if I heard your average English speaking person say them I would interpret them the same. Every time I’ve heard someone actually use the equivalent of S, it’s intent has been the equivalent of Q.
On the other hand, there are some situations where Q might mean something different, for instance, if they were talking about a ball player whose only skill is running quickly but could not do anything else, thus could “only” “run quickly”, where “only” implicitly refers to the subset of actions desired in that particular conversation. But the clarification (“alternatively, billy cannnot run slowly”) means that we should ignore this possible meaning of Q
Yeah, sure, but in that case, the same thing would be implied in S. If the context (e.g. “only runs quickly”, “runs only quickly”) is present in Q, it’s present in S, and vice versa.
Headache from reading all the interpretations - so I will just give mine, sorry if it’s a repeat.
S. has just one meaning – he has no alternate state to running quickly. He runs quickly at all times and in all situations.
The two statements in Q are not exactly the same:
Billy can only run quickly. 2) [Alternatively: Billy can not run slowly.]
If the sentence means he can “only run quickly”, that could mean there is no situation where he can not run quickly. He can’t stand still, for instance. That interpretation would be the same as S.
To say he can not run slowly, however, does not eliminate the possibility that he can do other things besides run, in which case S. does not follow. For accuracy, this might be better stated as “Billy can run only slowly”, but grammatically correct or not, this is not a typical construction.
Since the second part of Q is not equal to S, then neither is the whole thing.
This thread makes me dizzy. Everyone is making this more complicated that needed. Let us use the words “cannot” and “can not” interchangeably for a moment, shall we? Let’s also say that the use of “only” in “q” refers to Billy’s running, and not every other aspect of his life.
p: Billy can run quickly. - Billy is capable of running quickly. Doesn’t mean he always does, doesn’t mean it’s the only thing he does, doesn’t mean much other than Billy has the ability to run fast. q: Billy can only run quickly. [Alternatively: Billy can not run slowly.] - When Billy runs, he can only do so quickly. He is not capable of running in any way but quickly. r: Billy can not run fast. - Billy is not capable of running fast. If he tried to run fast, it wouldn’t work. s: Billy can not not run quickly. - Not running quickly is not something Billy is capable of. He is not capable of running in any way but quickly.