Mustn’t not must, instead, must not.

Got something weird for you today, which came up on the forums a little while back. Have you ever tried telling someone that they don’t have to do something, or that they have to not do something?

Well if you do in Esperanto, you could be in for some head scratching and confused grunting, or be the cause of said scratching/grunting in another.

Let’s start with an easier example: telling someone they cannot do something and telling someone they can not do something if they like.

  1. You cannot feed her = Vi ne povas manĝigi ŝin
  2. You can not feed her (if you like) = Vi povas ne manĝigi ŝin (se vi volas)

See how 1 is just a simple negation of the verb. Without the “ne” (vi povas manĝigi…), this would mean, “you can feed her / you are able to feed her”; you have the ability to feed her. With the “ne” in front of the verb, like negating any verb,  this is reversed: you don’t have the ability to feed her; you cannot feed her, you are not able to feed her. In other words, the ability (to feed) is missing.

But in 2, the verb is not negated at all! Since in order to negate a verb, you must place the “ne” before it. So here, you most definitely do have an ability, you are able to do something. And what is that something? To not feed her.

This shows how the “ne” derives different meaning very logically from its placement. I’m happy with this!

But the reason for this post is that the behaviour of the verb “devi” (to have to / to must) leaves something to be desired. It has acquired a meaning in negation which is quite unruly. I can understand why, but I don’t like it, and have a suggestion for how to get people out of the habit, without breaking any rules, so that eventually tradition may change.

Well, let’s get started:

a. You don’t have to feed her
b. You have to not feed her / You must not feed her

How would we anticipate that the above are translated into Esperanto?

In the previous discussion “povi” was talking about “ability”. 1 was the lack of an ability to feed her, and 2 was an ability to not feed her.

We’ve got exactly the same problem here, except that instead of “ability” we have “duty”. In example a, we have the lack of a duty; you don’t have the duty to feed her. And in example b, you do have a duty, and the duty is to not feed her. So, logically, a negates the verb of interest (says that there is no duty, no “devi”) and b negates the feeding that follows (not the duty). Thus we’d expect:

a. Vi ne devas manĝigi ŝin = You don’t have to feed her
b. Vi devas ne manĝigi ŝin = You have to not feed her

But chances are, most readers would read both of those examples as “you must not feed her”!

What the jam!?

Now, I dunno about other languages, but I can certainly see at least one reason why English speakers might naturally keep falling into this behaviour. And that’s the fact that “devas” can translate as “must”. If “devas” could only mean “have to”, then a would clearly be “you don’t have to…” and b would be “you have to not…” because of the “ne” placement, and thus the distinction is made easily.


When “must” craftily creeps in, as it often does, we’ve got a problem, since we don’t say “you don’t must feed her”. We always switch to “don’t have to”. But if the reader is translating “devas” as “must”, then both a and b legitimately seem to say “you must not feed her”, since a is negating “must”, and b is following the more usual English word order of “must” usage.

Interestingly, as the PMEG reveals, Zamenhof himself confused these usages often, using both with the “you must not feed her” meaning (the “devas ne” meaning), so the issue is certainly widespread. The PMEG suggests this might be due to this being the most common meaning required, and that “ne” before verb is the most common style of negating.

When Zamenhof wanted the “you don’t have to feed her” meaning (the logical “ne devas” meaning), he used a completely different verb: “bezoni” = “to need”:

  • Vi ne bezonas manĝigi ŝin = You don’t need to feed her (You don’t have to feed her).

Buuuut bitter-sweetly, Esperantists are apparently beginning to see the logic and use the “ne” placement logically. But this means we’re in a situation where we have to decide whether the writer/speaker is aware of this problem or not, because if he/she is, then we’d interpret “ne devas” one way, and if not, the other!

Of course, if you have the luxury of speaking instead of writing, you could try to use intonation to get across which meaning you’re after. But would everyone interpret you the same way?

What to do? Especially if you want to encourage the newer logical usage without making unwelcome sweeping changes that aren’t understandable to traditional speakers?

My idea is the following:

I will never use “ne devi” in that order until the new logical usage is standard. Simply because, in Zamenhofian usage, it means one thing, and in the growing more logical usage, it means another.

Instead I will use “devi ne” since in both usages it means “must not / have to not”. And I will use “ne bezoni” to mean “don’t need to / don’t have to”. Since again, in both usages, this is unambiguous.

So with this tactic, not only am I following Zamehofian tradition, but my works will also be understandable to those with knowledge of this nuance. If we all did this for long enough, perhaps “ne devi” would fall out of use in the old way, and eventually make a return in its logical usage? One can hope 🙂

The inspiration for the discussion in this post (especially the usage of the words “missing” and “lacking” to explain the logic) is the PMEG post on this matter. See


6 thoughts on “Mustn’t not must, instead, must not.

  1. I like this kind of setup:

    a. Ne necesas ke vi manĝigas ŝin = You don’t have to feed her
    b. Necesas ke vi ne manĝigas ŝin = You have to not feed her

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