Can't have been vs. coudn't have been

FallenOneI wonder why we have "can't" here?

"can" is present tense, "can't" is past. "can't have been" = "can not have been" which express a past probability.

FallenOneWhy not couldn't have been with him?

This is also correct.

FallenOneOr why not just couldn't be with him?

thanks, but I thought "couldn't" was past. I'm really confused now. "Can" is present then why "can't" is past? Can't it seem to be present either?

FallenOne,

Can - is affirmative present.

Can't is negative present.

She couldn't have been there because I was with her the whole time. This is apparently a past context, so "can't" is not a logical, nor is it a syntactically sound answer in my estimation.

Thank you too. Why did MalRey say that "can't" is past? Do you mean that we can't use can't have been in the past? Is it could have been only?

FallenOneWhy did MalRey say that "can't" is past?

He was incorrect.

Why do we need to say "can't have been"? What do we mean by that?

FallenOneJenny can't have been with him at that time, for I was having dinner with her in my home.
I wonder why we have "can't" here? Doesn't "can" refer to the present tense only? Why not couldn't have been with him? Or why not just couldn't be with him?

can't have been = is impossible that ... was ....

It's the 'have' that makes it past. You mi

As I understand it, "can't have been" can only refer to the past events. I can't have been that bad = I couldn't be that bad?

Thank you for answering!

FallenOneI can't have been that bad = I couldn't be that bad?

No.

Let's say you already tried to do something, but you didn't do it very well. A friend says, "You really did poorly with that task". You say, "I can't have been that bad". That's saying that you don't believe you did as poorly as your friend claims.

Now let's change it. Suppo