Couldn't : Didn't: Any difference?

[Jesus1]

Hello! How are you! Thanks in advance!



1.- "The doctor told me the checkup was fine,
But I COULDN?T believe him".

2.- "The doctor told me the checkup was fine,
But I DIDN?T believe him"

Should I use the second sentence if I meant:
A)))"I didn?t believe the doctor ?cause I thought
he or something was wrong"?



I ask you ?cause I think my
first sentence has to do more with
surprise!
It is as if it was impossible to me to believe
the doctor?cause I was shocked by the
good news.
Maybe not. I don?t know. Perhaps, I can
use it as well to mean what
I said in the point A))), that is to say,
"I didn?t believe him ?cause I thought
he or something was wrong". Can I?
Do both of them mean the same?

Thanks a lot!

Jes?s

[Alan]

Hi Jesus1,

No, they are quite different. I didn't do it is the past negative form of do and means simply that something was not done by me.

I couldn't believe it means I was not able to believe it - it was not possible for me to believe it.

The one thing that they both have in common is that of disbelief.

I didn't believe the doctor means simply I didn't think he was telling me the truth.

I couldn't believe the doctor means it was very difficult for me to believe what he said because it didn't seem possible to me.

Alan
_________________
English as a Second Language
You can read my ESL story A funny thing happened...

[Alan]

Hi,

Another thought occurs to me. As used in conversation you could well say: I don't believe you! suggesting that there must be a mistake. As in:

A I've just won the lottery

B I don't believe you! You must be joking.

Alan
_________________
English as a Foreign Language
You can read my EFL story Word Story: Dictionary