To my knowledge, both How could I...? and How could I have...? can be used to express disbelief at something you did in the past or you have just done. What could be the difference, if there is any?


could is for past ability. (We're not using it as a conditional clause.)

How could I do this? (I did it and I'm asking myself this.)

could have is for past possibility.

How could I have done this? (There was a way to do this, but I didn't, so I'm asking myself this.)

  • But couldn't we say, "How could I have done something so stupid?" when we really did/have done some insensible act?
    – goldbrick
    Nov 27 '15 at 17:27
  • If you did it, you use How could I do something so stupid?
    – Schwale
    Nov 27 '15 at 18:02

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