Here are two sentences extracted from the Harry Potter series:

1, The harder she tried to pull it(a sweater) over his head, the smaller it seemed to become, until finally it might have fitted a glove puppet, but certainly wouldn’t fit Harry.

2, It(a snake) could have wrapped its body twice around Uncle Vernon's car and crushed it into a trash can -- but at the moment it didn't look in the mood.

My question is, why we should use 'might/could have done' structure in these sentences instead of 'might/could', and why 'would have done' structure is not used in ‘but certainly wouldn't fit Harry’?

  • why we should use 'might/could have done' structure in these sentences instead of 'might/could' The use of "might/could have" vs. "might/could" is addressed in many grammar books, websites, etc., including this site. Please describe the resarch that you did and why that didn't answer your question. Feb 23, 2023 at 4:46

1 Answer 1


The Harry Potter books are written in the past tense (crushed; it didn't ...) But "might" and "could" don't have proper past tense forms. So the perfect stands in when describing events in the past.

The use of these perfect would have been possible as in "wouldn't have fitted". The choice of tense here is stylistic. The author is choosing to switch to a general fact, not speak about this as a past condition. You would have to ask JK Rowling why. It probably works slightly better as a joke the way she has written it, as the change in viewpoint makes it more direct.

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