What's the difference between these two sentences?

How could you do this to me?
How can you do this to me?

If a friend is stealing or stole from me, which would I say?

  • One is past, the other is present. – Yosef Baskin Jul 25 '17 at 4:37
  • @YosefBaskin Or conditional. – Dog Lover Jul 25 '17 at 4:39
  • you could also pre-empt and use 'would' – JMP Jul 25 '17 at 4:48

Can is the present tense, could is the past conditional. Depends on how precise you want to be. The infinitive of this orrid verb is "to be able to". Only English could feature a verb with an irregular infinitive. Technically, if the harm is still ongoing (progressive) you would use "can". If it was a single past event with no ongoing effect you would use "could".


The natural way to read the could here is a past tense. That means that your two sentences come out as:

  • How were you able to do this to me?
  • How are you able to do this to me?

The difference, then, concerns when the action took place. If you're talking about something that was done some time ago, as a one-off, then the first would be better; if it's something that the other person is still doing, then the second would be better.

In terms of your specific case, you say is stealing or stole, so it's hard to know... if your friend stole something a week ago, and you've only just discovered it, but there has been no repeat, then I would go with could. If you've discovered that your friend has been stealing frequently from you, and is showing no signs of stopping, then I would go with can.

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