He can't/couldn't be the wanted man.

It can't/couldn't have been true.

Why are can't and couldn't alternative in cases above?

Alex can't have broken that window because he never came anywhere near here yesterday.

  • In this sentence, could can't be replaced by couldn't ? Is there anything to do with the tense concord?

  • What's the difference between can't have done and couldn't have done ?


1 Answer 1


In those short sentences you give as examples, they can be interchangeable for normal, everyday use. That they are interchangeable here could be due to insufficient context around the sentences. Can versus could is more subtle than may versus might, or can versus may. Could is more subjunctive, tentative, but can is more firm - at least in this context.

  • As a follow up, wonder if our British speaking friends have a different take on this ? Commented Sep 5, 2013 at 2:41

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