Job Discussion Forums

[johnslat]

Dear Capergirl,
If you'll go to that web site I posted and scroll down, you'll see "can't have". You'll find it under "Probability (logical - guessing). I've seen and heard it used; heck, I've used it myself. But I agree that "couldn't have"
is almost certainly used more often.
Regards,
John

[leeroy]

[Deborah]

I think "can't have" is a rather British useage - is this correct?
I'd say "couldn't have." But I've taught both!!
"She can't have seen me."

[khmerhit]

You can't not have taught 'can't have'.

[Shaman]

I'm going out on a limb here, but could the difference between the two usages be explained as follows:

"She can't have seen me." Can't points to how the situation is affected in the present.
- eg. "She can't have seen me because she hasn't stopped walking."

"She couldn't have seen me." Couldn't points to the past.
- eg. "She couldn't have seen me because I wasn't there."

I must admit, I use the second example more often - stylistically, not thematically.

Shaman

[Capergirl]

[johnslat]

Dear Shaman,
ZZZZZZZ - sounds of that limb being sawed off. Nope, the "can't have", as that web page (which, however, many can't have looked at) that I supplied mentions:

"These modals + have usually indicate past uncertainty, NOT "perfect" aspect)

MEANING: Impossibility

PRESENT/FUTURE: can't/couldn't

PAST: can't have/could(n't) have

I'd say can't have/couldn't have are interchangeable and that either would work in the examples that you gave.
Regards,
John

[tammy]

Hmmm..
I tend to use 'couldn't have' for impossibility and 'can't have' for uncertainty.

He couldn't have seen Claire at the party because Claire's dead.
He can't have seen Claire at the party because Claire doesn't usually go to parties.

But I guess John's right.. can't and couldn't are interchangeable in both sentences.
I forget my point..

[johnslat]

Dear Capergirl,

"Oh, come on! "Can't not have"? Is that even English??? "

Of a sort. But I think khmerhit should have written

You can't have not taught "can't have".

or, better yet

You must have taught "can't have".

Regards,
John
P.S. Modals are the very devil to teach and test. They're usually taught as grammar, but I think they really belong in reading/vocabulary. There IS some grammar - present, past and perfect modals - but most of what's really important is meaning. And that depends SO much on context. "Could" is, I'd say, the worst of the bunch, having loads of different meanings.
Regards,
John

[bayabule]

Capergirl wrote

[johnslat]

Dear bayabule,
It's the contraction itself that causes the "writing confusion". The "'ve" in "could've", "might've", "should've" SOUNDS like an "of". So it's not surprising that the mistake is fairly common.
Regards,
John

[bayabule]

Hi John,
Yes, that's why I think it's just laziness of speech on my part as I'm quite aware of the correct pronounciation, but it keeps on slipping out.
I'd never use it in writing.
Cheers.

[Shaman]

Dear John,

I had it figured that the usage was subjunctive and not perfect. I inadvertently forgot to include the third option that you so kindly provided (interchangeability).

Oh well. Luckily the limb I chose to tread upon wasn't too far from the ground. I landed on my head, so I can't have incurred any serious injury.

Regards,

Shaman

[Stephen Jones]

[Capergirl]