Consider the following sentence:

If I knew what the problem ___, I would be able to help you better.

Should the verb be "is" or "was"?

1 Answer 1


That sentence is in the irrealis mood, and is commonly known as an "unreal conditional". In irrealis mood broadly, it is always correct to use a verb tense that is one tense in the past from the time they represent.

So in your sentence, the time is present, so it's definitely correct to use the simple past "was" to indicate it is unreal.

Sometimes we can also use the same tense as the time in unreal grammar. This is possible (never required) when the verb refers to a general fact or a long-term state. For example:

If I knew what his job is, I would be able to help you better.

In that context, his job is a long-term state, so "is" is acceptable. In your example sentence, however, "the problem" is probably just a problem now, not a stable, long-term state, so only "was" is correct, not "is".

  • I don't see the relevance here of Irrealis. Present-day English does not have an inflectional mood system; it was lost in earlier stages of the language. Leaving aside the modal auxiliaries, all that remains is what grammarians now call irrealis "were", which is limited to 1/3 sg forms of BE, as in "If he were in love with her, he'd change his job".
    – BillJ
    Commented Sep 11, 2023 at 8:58
  • Thanks for the explanations. Can you suggest a grammar book that deals with such nuanced details?
    – Long Horn
    Commented Sep 11, 2023 at 13:47
  • @BillJ That might be true for the term "irrealis" in current academic linguistics, but this is how it's commonly used in TESL.
    – gotube
    Commented Sep 11, 2023 at 18:43
  • It has nothing to do with "current academic linguistics". At any level of learning, it's obvious that there is not a single verb in English that is inflected for mood. The only odd-ball is irrealis "were" (or the ill-named past subjunctive) which is limited to 1/3 sg forms of BE. It's an untidy relic of an earlier system.
    – BillJ
    Commented Sep 12, 2023 at 6:42
  • @BillJ I don't want contested definitions to to distract anyone from my answer, which isn't about the meaning of those words. If I remove the word "irrealis" and replace it with, say, "unreal", would that resolve the issue?
    – gotube
    Commented Sep 13, 2023 at 5:18

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