BUT (conjunction)

  1. that (used esp. after words like doubt, deny, etc., with a negative word like not):

I don't doubt but you'll do it.


Isn't the example ambiguous with the alternative meaning "the only thing I doubt is that/whether you are able to do it"?

  • There is no alternative meaning. It is not: I doubt that you'll be able to do it.
    – Lambie
    Jun 29, 2021 at 12:34
  • "I don't doubt anything but (except for) you'll do it." - I don't know how grammatical and common it is, but it would require anything. Jun 29, 2021 at 12:50
  • @AndrewTobilko can you elaborate? For what meaning exactly?
    – GJC
    Jun 29, 2021 at 12:52
  • @GJC e.g. She is anything but nice (She isn't nice), I don't do anything but sleep (I sleep all the time). In my (questionably reasonable) example, it would mean "I really doubt you will do it". Jun 29, 2021 at 13:07
  • @AndrewTobilko No, anything is not required and that is really not very grammatical. I don't understand why these things have to be dragged out when it is patently clear to a native speaker that there is nothing ambiguous about: I don't doubt but you'll do it. for: the fact you will do it.
    – Lambie
    Jun 29, 2021 at 13:07

2 Answers 2


This case of the word but isn't used very often (at least not by me). You can say:

  • I don't doubt but you'll do it.
  • I don't doubt that you'll do it.
  • I don't doubt you'll do it.
  • I have no doubt you'll do it.

They all have the same meaning. You just won't hear the first one very often.

  • Right, and it will never mean: be able to do it. Nothing about being able at all.
    – Lambie
    Jun 29, 2021 at 13:06
  • What does I doubt but you'll do it mean then? _When the main clause is negative or interrogative, doubt could also formerly be followed by but that _ books.google.es/…
    – GJC
    Jul 18, 2021 at 15:22

This usage of but is so unfamiliar to me that I had to look it up in the Oxford English Dictionary. The example you cited corresponds to sense C.9b in the OED:

but, prep., adv., conj., and n.2

C. conj.

Ⅱ. In a complex sentence, introducing a subordinate clause.

  1. After various verbs in negative or interrogative constructions, reversing the effect of the negative or interrogative so as to affirm more emphatically the dependent clause (e.g. I don't know but she's got notions into her head = ‘I think it likely that she's got notions into her head’). Frequently in but that.


      (a) After verbs and verbal phrases expressing mental affirmation, as believe, be sure, conceive, conclude, persuade, say, see, think, wit, and (esp.) know. Now rare (chiefly regional).

      (b) After deny. Now rare.
    In this use, but has the effect of affirming the dependent clause without cancelling the preceding negative.

    b. After verbs and verbal phrases expressing dubiety, as doubt, despair, scruple. Cf. sense C.9d.
        [Compare classical Latin non dubito quin ‘I don't doubt that’.]

        1932 R. Macaulay: Shadow Flies i. xviii. 159. No question but the witch'll walk, starkling all the countryside.
        2009 P. Glennie & N. Thrift: Shaping the Day ii. 56. There is no question but that the striking of the clock would have been familiar to Roger Martin.

    c. After verbs and phrases expressing prevention.

      †(a) After God forbid, and similar expressions. Obsolete.

      †(b) After hinder, prevent, restrain, etc. (now followed by from with the gerund, or the gerund alone). Also after fail, forbear, hold, etc. (now followed by an infinitive or gerund with or without from). Often with infinitive as verb of the dependent clause. Obsolete.

      †(c) After I see not or I see no cause. Obsolete.

      †(d) After there wanted but little. Obsolete.

      (e) After cannot help (see HELP v. 11b).

    d. After fear and †dread. Cf. sense C.9b. Now rare.

Basically, it's saying that this usage of but really is uncommon, and becoming archaic, if it isn't already. Even their most recent citation prefers but that for clarity. I think most people these days would simply prefer that without but.

  • oed.com/oed2/00030107
    – GJC
    Jun 29, 2021 at 15:09
  • 2
    @GJC I cited the OED Third Edition (2018). In the Second Edition (1989) that you linked to, it's sense 21. Jun 29, 2021 at 15:15

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .