Can...past reference?

[Metamorfose]

I was thinking today when teaching, is it ever possible to have can to past reference? I can't think of any good example in English that I can make use of (instead of will which doesn't surprise me anymore.)

What do you say?

José

[JuanTwoThree]

Do you mean "can have + past participle"? .
Retrospective permission? Retrospective ability?
The only way that occurs to me is this:
"It can't have snowed last night"
"Oh yes, it can*. It often snows here in September."

(*have snowed) which is hardly what you'd call a normal situation. Apart from that rather odd and desperate example, I agree with you completely.

[Metamorfose]

JTT wrote

Do you mean "can have + past participle"? .
Retrospective permission? Retrospective ability?
The only way that occurs to me is this:
"It can't have snowed last night"
"Oh yes, it can*. It often snows here in September."

(*have snowed) which is hardly what you'd call a normal situation. Apart from that rather odd and desperate example, I agree with you completely.

Yes JTT I was thinking about restropective permission and/or restrospective ability, guess could does its task very well in this case. Good example of yours, logical deduction about something that has occurred (or what shouldn't have occurred).

Let me try it:

A:She can't have said all those things.
B:Surprised? Don't you know her enough?

Great! Thanks!

José

[JuanTwoThree]

"can't" the negative is a very different matter. In these cases it is more or less the opposite of "must":

Judging from the angle, the murderer must have been left-handed
Judging from the angle, the murderer can't have been right-handed


The question is if "can" the positive can be used in a modal perfect.

[Metamorfose]

Writing something on passive I did:

In this case a dummy subject is introduced – somebody. Here although we do not know who stole the camera the active sentence presupposes “an unknown, but knowable person”, it is possible to get to know who stole the camera, the choice will depend firmly on the speaker’s point of view, the stolen item or who can have done it.

Always on the ground I am not a native speaker nor do I live in an English-speaking environment, do think this (who can have...) is possible? Am I forcing language to fit into the 'rule'?

On the BNC (now I am powered) I found 8 examples with 'can have done'.

José

[JuanTwoThree]

I'm really not sure. Your example might sound better with "could" or "may" in place of "can" but to say your English is incorrect would be a stretch.

Those 8 (well 7 because 2 are the same) results:

It was an unhappy and tense discussion and can have done absolutely nothing for Geoffrey Howe's morale as he prepared for the afternoon.

Few men can have done more to relieve human suffering, or shown less interest in profiting from the process.

He was a successful president not because he `;focused'; --; few men can have done so less --; and not because he was the `;great communicator';, but because he knew who he was and what he believed in.

No one can have done more for the historian studying Islay than Mrs Lucy Ramsay ...........

No one can have done more for the historian etc

Something hardly anyone else can have done.

What on earth can have done that?';

Who can have done this evil thing?';


Maybe modal perfects with "can" are possible in some situations after all. Eight is not a lot of hits though.

"What can I have done with my keys?" sounds reasonable.

I'd bet that on 99.5% of the occasions when "can have done" is used by learners it's misused. So it might be a convenient white lie to say that such a thing does not exist.

PS 24 hours later:

I see that all the corpus examples bar the last two are negative or restrictive (is that the right word?): nothing, few, less, no one, hardly anyone.

"can have done" works ok in those questions though.