Cannot vs. can not

There is a grammatical misunderstanding common to many U.S. Americans, largely because we learned about grammar in the either/or terms of right vs. wrong. Here’s the misunderstanding: can not or cannot? My public school teachers said can not was the correct form, and that cannot was a corruption. A friend of mine from a previous generation was taught the opposite. Her son, much better at using the language than either of us, said both were right, but usage depended on context.

Here’s the explanation: If I can not do something, then I can also do it. I can not write these words if I choose (and you may think I shouldn’t), but I also can, and am, writing them. What I cannot do is know who will read them, or what they will think. I can imagine such things, but I’m limited by my experience and perceptions. So this is the rule: if you either could or could not do something, then you use two words, because you can leave out the second word if you so choose. If you could not do something no matter how much you desired or tried, then you use one word, cannot. There is no other option.

Sometimes both are true. Witness:

I cannot change the world.

I can not change the world.

It’s true, I cannot change the world. What I mean, and what many mean when they say or think this to themselves, is that the world’s problems are too big for any one person, or group of people, to take on. Poverty, sickness, hatred, love, weather, earthquakes, political and religious differences—these are inevitable conditions. Even Jesus said, “the poor you will have with you always,” and, “Let the dead bury the dead.”

It’s also true that I can change the world. I, and every other person on the planet, can make a difference. We can give to the poor, and try to cure ourselves of the sickness of wealth (more on that later). We can be courteous, we can provide emotional (listening) or physical (assisting) or financial (donating) help to others, we can feed and help and forgive each other. (More about forgiveness later, too.) We can take in an abandoned dog or cat and give it love. We can plant a garden. We can put in a day’s work and know we earned our pay, and someone, hopefully, was the better for it. We can not cut off someone in traffic. We can dedicate our lives to healing. We can dedicate our lives to loving our family and community. We can respect the differences of others. In other words, what we can do, we can do.

Grammar is the tool we use to communicate and should be taught as such. Our bodies, our minds, and our voices are the tools we have to interact with our universe. We must use them while we live; we cannot evade using them except through death or dire injury. In this sense we cannot not change the world. And now, while the world suffers on every level, from the sky to the deeps of the sea, from humans to tiny coral polyps, we can make what time we have count.

Don’t berate yourself for previous behavior. Don’t congratulate yourself, either. Just take the next opportunity to make a difference to the next person, and help make what we cannot change bearable.

29 December, 2003

Further discussion

6 January, 2009

Occasionally I get emails from people in response to this, ranging from pleased thanks to detailed explanations of why the option cannot be other than “can not” or “cannot.” Recently one of these linked to, a site dedicated to improving English skills.

I dipped into the site and found a message board with varying perspectives, and replied, signing up as “Logical.” The discussion was fruitful (among other things, I got a nice refresh on modals). Below are some arguments against using both forms in different contexts, along with my response, drawn from this discussion and email exchanges. (Read the English-Test discussion in full.)

  • The two forms mean the same thing, so we should just pick one and use it.

    The point of grammar is to make sense, and making “cannot vs. can not” an either-or situation ignores the logic of the words themselves. They are two different forms, and therefore necessarily mean different things. “Cannot” means it cannot happen at all. There isn’t a “can” option to contrast to it. I cannot go back in time, for example. The reason we don’t have an equivalent “shouldnot” or “mightnot” is because the essence of should and might doesn’t lend itself to this option. “Can,” though, readily implies its absolute opposite.

    “Can not” means it might happen; it can happen, or it can not happen. I can not post this comment if I choose. If you might not do a thing, then you can choose not to do it. So a person can say, with perfect consistency, “I can not do that, therefore I might not do that.”

    The very fact there is such a debate over this should be taken as a symptom that there’s a problem with the either-or scenario. It simply doesn’t make sense to restrict the language artificially, in order to force an illogical rule (whichever rule you learned). If it doesn’t make sense, it’s not good grammar.

  • The scope of the negation is the same in both, because “not” or “-not” belong to the following verb phrase

    Thanks to OxfordBlues on English-Test.Net, because this argument forced me to think things through more deeply.

    The idea is that “can” is apart from the “not _____” portion of the statement, whether in “cannot” or “can not” form. But it seems to me that if “not” is a syllable within the word, rather than a word following it, then it clearly belongs to the word itself, not to a subordinated phrase. This implies “cannot” bears a different meaning from “can not.” The ability of “can” in “can not” to exist without the word “not” implies there is an alternative state to not being able to do a thing, just as the permanency of “-not” in “cannot” implies no alternative.

    OxfordBlues suggested using a version of “be + able” to evaluate the difference in forms. To me, this made sense with “cannot” but not with “can not”, which demonstrated my point:

    David cannot drive. (David lacks the skill set for driving.)

    David is not able to drive. (This accurately describes David’s state.)

    Caroline can not drive. (Caroline could drive, but can choose to let someone else do it, or to walk instead.)
    Caroline is not able to drive. (This doesn’t accurately describe Caroline’s state.)

    Applying “will” options looks like this:

    David will not be able to drive. (Perfectly accurate.)
    Caroline will not be able to drive. (This doesn’t accurately describe Caroline’s state, since she might very well be able to, but choose not to do so.)
    Caroline will not drive. (This only works if it has been decided Caroline will not drive.)

    After much discussion, Bart (my husband, a much more accomplished scholar than I am) suggested the following sentence, which I submitted to English-Test.Net for feedback:

    I cannot not pay my rent and live in my home.

    Alan, the charming co-founder of the site, responded, “This to me suggests that non-payment of the rent is an impossibility for me. Surely in that case ‘can’ and ‘not’ are joined at the hip.”

  • Separating out the not from the word is merely an emphatic form with the same meaning.

    There are two arguments against this:

    • Emphasis is, for the most part, not written down, apart from the occasional bold-faced or italicized rich text formatting, or in eye-dialect. There’s nothing to stop emphasis from being added to either form by a reader or speaker. Interpretation of emphasis is dependent on context and the individual reader or speaker.
    • This is not a rule used in other verbs that I can discover, but a rationalization springing from lack of understanding. For example, the emphatic nature of the sentence, “I will not do that” depends on what is being refused. “I will not take the bus” is quite different from, “I will not murder.” The sentence stands well enough on its own, which is probably why we’ve never developed the form, “I willnot do that.”


  1. doofus says:

    Saying it CAN not happen is silly. Of course… anything CAN not happen in any context. Just some pointless BS for professors to bring up to impress the students.

  2. Susan says:

    Thank you so much for this very helpful information!

  3. W. Volterman says:

    “I can not eat something.” or equivalently “I can’t eat something”

    “I can, not eat something.”

    I don’t need “cannot” in order to separate the two ambiguous meanings, only punctuation.

  4. mk says:

    I say, let’s just use “can’t” and forget the other nonsense.

  5. David says:

    So when can I use “can’t”? Can I apply “can’t” to can not and cannot?

  6. Bernard Scahill says:

    I teach my high school students to distinguish between the two forms in the way you have suggested, but there is something I add. There are times and situations in which I can not bring myself to say or do something; for example, I just can not bring myself to compliment my boss. That form is a bit like the present tense version of “could not.”

  7. Callie says:

    This is giving me a headache. I thought I had found an answer but after reading the debates I find I cannot bring myself to care any longer.

  8. Jake Guenther says:

    Very useful information, thank you. However non of this information help me. I live a simplistic life and would prefer to not be wrong, rather than be correct. If I can not determine which is the correct version, I would like to at least not be wrong. My feeling is that I will continue to use “can not” rather than “cannot” simply due to the fact that it CAN be interpreted differently. The reader MUST determine the actual meaning from the rest of the context, just as when spoken.

  9. I was wondering what the difference was between cannot and can not or if one was correct and the other wasn’t. I found this article to be very good at explaining the difference. I hope it’s right because that’s what I’m going by from now on.

    Thank you,


  10. msan says:

    I think of it this way: the word “can” has to do with ability. “Cannot” would be the same as “unable to” where as “can not” would be the same as “able to not.” There’s a big difference.

    I cannot (am unable to) live without oxygen.

    I can not (am able to not) pay my rent so that I could buy this TV. However, if I did not pay rent I would be evicted.

    In the first sentence the person is physically unable to live without the oxygen. It would be wrong to say, “I can not live without oxygen.” That would be saying that you had a choice to live without it or had the ability to live without it.

    In the second sentence the person is able to not pay rent if they wanted to. Any of us could choose to not do something like that and ignore the possible consequences. The person has the money and wants to use it for buying a TV rather than for rent. If they had said, “I cannot pay my rent,” it would imply that there is some actual inability to do so. Either they do not have the money, or don’t have access to the money, or got in a car accident when trying to bring the check to the apartment, etc.

    These are very different meanings. Generally speaking, when we use the contraction can’t we mean that we are “unable to” do something. Many times (in today’s common English) we will say that we are unable to do something that we actually can do. That would be using “cannot” or “unable to” in a hyperbolic sense. When someone says, “I can’t bring myself to admit that it was my fault,” they are not saying that they physically unable to say the words “it was my fault.” Neither are they really meaning to say that they are “able to not” admit they were at fault. Obviously they could choose to not take fault. The point of their comment is to make a drastic statement about how difficult it is to admit they did something wrong.

    Anyways, there’s a difference between the two and sometimes we are not speaking literally when we use “cannot” or “can’t.”

  11. msan says:

    Actually, in many contexts it would make perfect sense to say that something CAN not happen. The idea isn’t just in regards to something not happening but also could be applied to someone’s ability to not choose something. Take this for example:

    “I can not do my homework tonight, but that would mean I’ve got twice as much to finish over the weekend.”


    “I can not pay my rent so that I can get this TV. However, if I don’t pay rent I’d be evicted.”

    The issue is that the PERSON has the ability to make a choice to not do something, not necessarily that something CAN not happen. It’s not silly to use “can not” in that sense. In fact, people make those kinds of decisions all the time.

  12. alex says:

    You’ve got it!

  13. Alex says:

    “I can not do my homework tonight, but that would mean I’ve got twice as much to finish over the weekend.”

    This is incorrect. Change “can” to “could,” or change “would” to “will.”

    I contest that the former is the more correct option, as the completion of the homework is hypothetical.

  14. Jeremy says:

    Your friend’s son is correct. The distinction is particularly useful in logic. As you say, in ‘cannot’ the not modifies can. Whereas it modifies the following verb or phrase in ‘can not’. Thus:
    Cannot = ‘not possibly p’.
    ‘Can not’ = ‘possibly not p’ (which doesn’t curtail possibly p, or p).

  15. J says:

    “They are two different forms, and therefore necessarily mean different things.” <– This is a false assertion, and does not reflect the messy development of language. Cannot is a 15th century contraction of "can not", and carries a specific meaning (inability) in modern common usage. It certainly does not follow that "can not" automatically loses that meaning. "Can not" is ambiguous, historically speaking. However, the prevalence of the spelling "cannot" has won out over time in frequency (3 to 1, according to the Oxford Dictionary). The majority who chose "cannot" over "can not" or "can't", were and are still forced to use "can not" when using a meaning where "cannot" will not work. (As in the examples above) This probably explains why so many feel so strongly "can not" is limited in scope, or even an error.

    Some dictionaries are silent on the matter (Webster's), and some explicitly allow that "can not" has the same meaning as "cannot", but is less common (Oxford, Random House). I have yet to find a dictionary that specifically disqualifies "can not" as an error. Oxford does say "can not" is better used in limited situations, but that it is "acceptable".


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