Consider this example:

A few strong branches over water reach for what they ought not reach.

Which of the meanings comes closest to “ought not” in this sentence?
Is it “doesn't have to”, “should not” or “must not”?

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    Verbs like ought, should, must, have to express degrees of desirability or probability, neither of which really apply to non-sentient things like branches. Maybe the branches "ought not reach" according to the writer's preconceived notions of whether they were likely to. Or maybe it's a type of plant that can extract soil-based nutrients from far-reaching branches (like weeping willows, I think). If the soil on the other side of the river contains toxins, figuratively the plant might very much "wish" not to reach across and thus poison itself. Commented Dec 31, 2011 at 16:29
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    All modals have intransitive epistemic senses about possibility and probability, and volitional deontic senses about permission and obligation. Deontic senses apply to people, but living things are borderline. All the interpretations FF offers work fine, in context, because modals underdetermine, like most semantics. Commented Dec 31, 2011 at 18:00
  • @John: Absolutely. I had no conscious knowledge of all this "underdeterminism" before I came to ELU. It's practically a weighty tome in itself, but I still really like this answer by Cerberus about the issue. Commented Dec 31, 2011 at 19:10
  • I forgot to mention that the negation is inside the scope of ought (to) in ought not to P; i.e, the logic is ▢¬P, although the square has rounded corners, as a weak necessity modal. This is the same as should not or shouldn't. I don't hear or use oughtn't, though I encounter it written occasionally, but it has the same semantics, too. Commented Dec 31, 2011 at 19:39
  • > Ought not Jason to have slept after working all day long. Compared to > Jason ought not sleep after working all day. With simple changing of the position of Jason, it changes the meaning.
    – user52152
    Commented Sep 16, 2013 at 11:29

5 Answers 5


Some might prefer the sentence to have to before reach, but otherwise it is well-formed. It’s impossible to be sure of the meaning out of context. It could be should not or it could be must not, or possibly something else, but not doesn't have to (which would in any case have to be don't have to in order to agree in number with the subject).

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    I agree ought not to do normally includes "to", but I can't say my "inner grammarian's ear" particularly pricks up if it's missing. On the other hand, I have to admit I'd much rather hear "to" included in "non-negating" constructions. Commented Dec 31, 2011 at 16:16
  • @FumbleFingers: I did wonder about it, but felt its omission here sounded a little precious. I have amended my answer to avoid suggesting that its absence is impossible. Certainly, a sentence such as ‘We ought not say anything in case we’re misunderstood’ is permissible. Commented Dec 31, 2011 at 16:23
  • Quite so. But ‘We ought say something lest our silence be mistaken for tacit consent’ doesn't really work for me. Anyway, now I can upvote the answer with a clear conscience. It's not a clear-cut sign of illiteracy to drop "to" in negating constructions - I wish I could have found an example from a well-respected author to establish that point, but it's an awkward one to search for. Commented Dec 31, 2011 at 16:57
  • @FumbleFingers: The OED has 536 citations for ‘ought not to’. There must be some from well-respected authors among them. I’ve only lighted on this from Rossetti: ‘we ought not to lack for adventures’. Doesn’t ‘ought’ always have to be followed by ‘to’ in positive statements? Commented Dec 31, 2011 at 17:04
  • No no - I was talking about 'ought not do' as opposed to 'ought not to do'. For which the Rossetti equivalent would be ‘we ought not lack for adventures’. Here are a handful of such, but "not lack" here bothers me a bit more than "not do". Commented Dec 31, 2011 at 18:33

There appear to be several issues entangled here.

One issue, the answer to the OP's original question, is that they're all different modal constructions, each with different sources, different syntax, different idioms, and different possible senses, which nevertheless often overlap, in the right contexts. And they're all irregular as hell.

Another issue is the metaphoric source of ought, which is, as many of us know, the old past participle of the verb to owe, and is caught up with the concepts of credit and debit, authority and duty. One ought to do something if one owes one's action (to some person, or some abstract principle) to pay a debt, to pay one's due(s), to do one's due-ty, etc, etc.

Ought (or more commonly oughta) is principally a weak Necessity deontic modal, like should, rooted in a Face and Credit social system (rather than a Strict Authority system, like the strong Necessity modals must and hafta) but there is an epistemic sense as well, usually functioning wherever emotions can be invoked or inferred, as in anger over a misplaced item. Compare

  • Dammit! It oughta be here.


  • Dammit! It should be here.

which sounds a little weaker to my ear by comparison. But that could be personal usage bias. There's a lot of that, with all modals.

Still another issue is the use of ought as a true modal auxiliary verb (which means no to on infinitive complements), or as a semi-modal auxiliary, (like need or dare, which allow to before infinitive complements, under certain circumstances).

Ought is a paraphrase of a true modal auxiliary (in this case should) that hasn't quite assimilated yet, at least not enough to lose the to everywhere. Like the true modal auxiliary should, it precedes not, but there are variant past constructions -- hadn't oughta, shouldn't oughta. Also like should (and would, could, might and must), it's formed from a preterite stem but can refer to the future naturally.

But should never takes to. However, ought, if it's separated from its infinitive by a negative, can suffer stack overflow, lose its modal binding field, revert to regular verb status, and allow automatic generation of an infinitive complementizer to. This alternation of ought not go vs ought not to go resembles the behavior of need and dare, which are also Negative Polarity Items as modals, though with a different syntax.

Outside negative polarity environments, though, the to in ought to seems likely to remain for a while. It is reinforced by the bisyllabic nature of all the periphrastic modal proto-auxiliaries oughta, hafta, gonna, wanna, etc, which are all in the same kind of boat, but whose individual grammars all leak in different places.

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    For a moment, I thought can suffer stack overflow was kind of a joke. Thanks for your analysis!
    – Dan
    Commented Jan 1, 2012 at 13:29
  • Stack overflow is one of the biggest dangers in conversation. We all know people with busted stacks or weird hashing algorithms. Commented Sep 19, 2013 at 17:31

In general usage, should not. "Doesn't Have to" does not really make sense to me in that context, whilst "must not" appears too strong.

A few strong branches over water reach for what they should not reach

However looking at that sentence it does seem a little odd. I am still confident that that is the best fit.


We normally say A few strong branches over water reach for what they ought not to reach.

I'd rephrase it as "... reach for what they aren't supposed to reach". The closest meaning to this is should not.


The sentence or line in reality comes from a song entitled, My Friends by Laura Marling. Click on Youtube to watch a rendition of her song.

Furthermore, the meaning and the particular construction of the sentence is clearer when seen in its original context.

The last verse of the lyrics copied from the website; Always on the Run.

A few good men will go where they ought
Where they ought not be
And a few good mothers go for what they
What they ought not teach
And I long for a touch a reminder of us but
But it must not be
And a few strong branches over water reach for
What they ought not reach

My interpretation of the line (similar to @Irene's) is that the branches touch or reach for what they ought not to touch or reach. In other words, the protagonist should not reminisce over a relationship which has reached its conclusion.

Edit: In view of @tchrist comment below, the form: ought not + verb (bare infinitive) is commonly used in the US and is considered grammatically correct.

However, consulting my trusted Practical English Usage by Michael Swan, the accepted way to make negative infinitives in British English is by putting not before the infinitive. For further reference see this question "Infinitives with ought not" posted in July 2011.

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    It turns out that ought not *to do something is ungrammatical in my own language, even though ought to do something is just fine. But with negation or inversion, the to particle disappears for me. I believe British English doesn’t mind the to there, but it isn’t something that I could/would/ought to say. :)
    – tchrist
    Commented Sep 16, 2013 at 18:05
  • @tchrist I didn't know that "ought not + verb" is the accepted form in the US, it appears that some grammarians would also agree with you. There's a question that handles this issue, the Ngram graph results, showing "ought not to go" being more popular were a surprise for me too!
    – Mari-Lou A
    Commented Sep 19, 2013 at 5:33

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