Can unless be used in "imaginary" conditional sentences?

Do the following sentences sound natural to you, native speakers?

Sentence one: I couldn’t have got to the meeting on time — unless I had caught an earlier train. Sentence two: Unless he were my friend, I shouldn't expect his help.

  • #1 sounds a bit weird to me because I usually expect past tense [not] X unless Y to be used in contexts where X is known to be true, so Y must also be true. As in "I wouldn't have married you unless I loved you". #2 sounds like an extremely dated/stilted (if not archaic) usage. Commented Jun 24, 2014 at 1:51
  • @FumbleFingers re #2 maybe it's the content which makes you say that? Unless I catch the bus, I'll be late is a perfectly natural construction. Commented Jun 24, 2014 at 2:01
  • @Esoteric: I specifically said past tense [not]. Your example is present/future[/imaginary?], and doesn't include negation. Commented Jun 24, 2014 at 2:12
  • @FumbleFingers you specified past tense for #1 (X unless Y), not #2. In #2 you've made a simple blanket statement, hence my comment. Commented Jun 24, 2014 at 2:13
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    @Esoteric: The possibility of putting the unless clause at the front makes no difference to me - it's just normal stylistic inversion. In my first comment I gave the more familiar version of OP's construction #1, which prompts me to interpret his text as "The fact that I got to the meeting on time proves that I must have caught the earlier train" (which is semantically a bit odd, to say the least). For #2, it's specifically the word were - which unlike you I don't see as equivalent to is in this context. Commented Jun 24, 2014 at 3:00

1 Answer 1


Sure, you can use unless in hypotheticals. Whether or not the situation has materialized has no bearing on whether or not you can use unless. Indeed, the purpose of unless is creating conditional clauses. Consider:

  1. A unless B
  2. Unless B, A

The constructions are ordered differently but have the same meaning; if one structure is transformed into the other, the semantics are preserved. In both cases, the statement says that B is a necessary condition for A; A is false if B is false, and B is true if A is true. However, saying that A is true if B is true a logical error. For example, your examples:

  1. A (getting to the meeting on time) is false if B is false, because this sentence tells us the only way to get to the meeting on time was to catch an earlier train (which is if A then B). But catching an earlier train does not guarantee arriving at the meeting on time; what if I forgot my briefcase and had to go back?

  2. Here, A is I should expect his help and B is he's my friend. This sentence says don't expect help from anyone who's not your friend (if not B, then not A). Note that just because he is your friend does not mean you should expect his help.

Notice that in sentence 2, B doesn't include not. Using not or not depends on the content of the sentence. Observe:

We will go to the park unless it rains. Unless it rains, we will go to the park.

Here, B is logically not raining, because the statement means if we don't go to the park, it must be raining.

If A then B and if not B then not A do in fact have the same meaning. For A to be true, B must also be true allows us to deduce that if B is false, A must also be false. See Wikipedia for further explanation of the logic of implication.

But the discussion of predicate logic is beyond what you've asked. Simply put, it's perfectly OK to use unless for imaginary conditionals. As for the sample sentences, your use of unless is correct. They don't sound quite natural, but in both cases it's a matter of conjugation, not conditional clause structure. Here's how I'd change them:

  1. I couldn't have gotten to the meeting on time — unless I had caught an earlier train.
  2. Unless he is my friend, I shouldn't expect his help.
  • I think your final "amended version" actually changes the meaning. To me, OP's version asserts that the only reason I should expect his help is because he's my friend (a known fact). Yours implicitly admits of the possibility that in fact he might not be my friend. Commented Jun 24, 2014 at 1:57
  • Am I reading your comment correctly? You're you saying that changing were to is changes the meaning? The original (were) makes a factual statement (he is definitely my friend) and using is instead means he might not be my friend? Because I vehemently disagree if that's what you mean. Changing the tense (to match shouldn't expect) has no bearing on the truth of the conditional (whether or not he's my friend), and the friendship is unknown in both cases (were or is). Commented Jun 24, 2014 at 2:04
  • I think it's hard for me to vehemently defend any particular nuance to OP's [subjunctive?] were, since it's probably a usage well before my time. And to my ear, unless there sounds even more "archaic/weird" than except, as in "He would not have been held except He were man". But we may have to non-vehemently disagree on this one. Commented Jun 24, 2014 at 2:28
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    Changing was to is in Sentence #2 was my immediate thought as well. For #1, I might've suggested change got to to made: I couldn't have made the meeting on time — unless I had caught an earlier train. (Ironically, we could add a "not" in there, and it would mean the same thing: I couldn't have made the meeting on time — not unless I had caught an earlier train.) Nevertheless, I think you've nailed it; +1.
    – J.R.
    Commented Jun 24, 2014 at 9:44

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