One of the use of would has been listed below:
You use would , or would have with a past participle, to indicate that you are assuming or guessing that something is true, because you have good reasons for thinking it.
⇒ You wouldn't know him.
⇒ His fans would already be familiar with Caroline.
⇒ That would have been Della's car.
⇒ He made a promise to his great-grandfather? That would have been a long time ago.
⇒ It was half seven; her mother would be annoyed because he was so late.
What I'm most confused(not understood) is as follows:
Use of would is just like the use of 'must' for drawing logical conclusion or presumption: for example:
*His fans would already be familar with caroline.
You mustn't know him.That must have been Della's car.
So, how would is different from 'must' in this usage ?
I would appreciate your helpful responses.Thank you.