Simple grammar question for native English speakers?

Question

Hi! Can somebody please tell me what the difference is between these two sentences:

1, She can't have told him yet
2, She couldn't have told him yet
and
3, The door can't have been locked.
4, The door couldn't have been locked.

Thanks a lot! :-)

Answer 1

The various proposed answeres are wrong when they suggest that 1 and 3 are incorrect. they are not common, and most people don't now use them, but they have been used in speech and in writing.

English verb tenses, particularly the complex ones (with the helper verbs), are numerous and often only subtly different. In this case the distinction is between a fact of reality (it can't have been which would presumably be discovered when actually confronting the facts and a conditional conclusion disproved.

His igorance in 1 is the fact, and the door's locked condition is the fact in 3. For 2 and 4 some investigation suggests that it ould have been impossible that because of something which turned up later. It turned out that he knew in 2, while something shows that contrary to expectation, some new fact shows that the door being locked is impossible.

Some languages, like Navajo, include in verb tneses information about the nature of the agent which caused the we are observing. One tnese for a fence knocked down by a windstorm, another for the same fence, knocked down to the same condition, by a living agent (cows, maybe). Englich complex tenses tend to convey information about probabilities and expectations as well as time values and conditionality (eg, subjunctive). for those who master them, the English tense system is a supple and graceful tool.

Answer 2

First, "can't" is a contraction for "cannot," which is itself a compound form of "can not." "Couldn't" is a contraction for "could not." So the question is, what is the difference between

1, She can not have told him yet
2, She could not have told him yet

The above two negative expressions can be cast as positive expressions, making them easier to analyse.

1, She can have told him.
2, She could have told him.

Clearly, the first is grammatically incorrect, and the second is grammatically correct. "Could" is the past tense of "can," and the past tense of a verb, not the present tense, is used in the past perfect tense with "have."

That is a definitive answer, from an educated American native English speaker.

Answer 3

1. She can’t have told him yet = She cannot have told him yet.
2. She couldn’t have told him yet = She could not have told him yet.
and
3. The door can’t have been locked = The door cannot have been locked.
4. The door couldn’t have been locked = The door could not have been locked.

Both nos 1-and-2 convey the same meaning, as also do the 3-and-4 pair !
...But, nos 1 and 3 are colloquial versions - used mainly in conversations. And nos 2 and 4 are the grammatically correct versions - but very seldom used while speaking.

Answer 4

While 'can't' is in the dictionary, it is not proper English. Unless of course you are speaking Ebonics, in that case every other word in the sentence is wrong...LOL. Anyway, numbers 2 and 4 are the correct ones. "have told" and "have been" are both past tense as is "couldn't" with is a contraction for "could not".

Answer 5

In both instances, the "couldn't" is grammatically correct. "Can't" (can not) is representative of a present situation (as opposed to past or future). Because the sentence has the adverb of "have" in front of the verb 'told", it is representing something that has already occured (in the past), therefore "couldn't" would be the appropriate choice. "Couldn't" (could not), represents the tense of past (past tense.) If the sentence said " She can't TELL him yet", then it would change the tense to a present tense and the word "can't " would be appropriate grammer.

Answer 6

It's a question of tense - 'couldn't' is past tense - you would say the door couldn't have been locked when you're talking about it after the event.

'can't' is present tense, you'd say 'the door can't have been locked' when you are at the door just discovering this fact.

Answer 7

Other than the fact that the first one is grammatically incorrect, the first one in each section is in the present while the the second one is presumably past tense. The word "can't" is not in agreement with the rest of the sentence. I don't remember much, but I know it's wrong.

Answer 8

You wouldn't really say, "She can't have told him yet." "She couldn't have told him yet." is better English. The word "couldn't" (as I'm sure you know) is a contraction, or a shortened version of "could not".

Same with the next two sentences: "Couldn't have been locked" is preferred.

Answer 9

What makes you think only native speakers are good at grammar. In fact, a lot of them are very poor in grammar. On the contrary, a large number of people who learn English as a foreing language are well versed in grammar.

Answer 10

The verb tenses do not match in 1 and 3.