This should be marked as correct, this isn't an English grammar course but a French as a second language course.
Also, regardless of 'correctness' if a professional translator was to translate that sentence he would use 'could' because the point of translating is for people to understand you.
Colloquially, yes. But some people still use the language more precisely. (It's tricky business because in "he cannot have read", he is formally the subject of can, but it's not really about his ability.)
This is a distinction that reaches far back in time and was standard among European languages until fuzzy thinking of some English speakers ("it's about the past, so I'll use past tense with all verbs") reached critical mass in some English-speaking areas. That is, so many people made this mistake, that a critical mass of children picked it up as correct. This is the point where a grammar mistake becomes a new rule. We are currently at the stage where this new rule coexists with the old one and slowly makes its way into written grammars.
The problem is that the English language is in the process of losing a distinction that can sometimes be important, and that is still made consistently in most other European languages, such as French:
- Il ne peut pas avoir lu ce livre. - He cannot have read this book.
- Il ne pouvait pas avoir lu ce livre. - He could not have read this book.
The above is how English has worked for many centuries, and it is still correct today. I hope the difference becomes clearer in context:
- He still doesn't know the contents of the book now. He cannot have read it. It is not true that he has read it.
- When I last met him a week ago, he still didn't know the contents of the book. He could not have read it. It was not true that he had read it.
The problem is that many native speakers have started consistently replacing 1 by 2 for no obvious reason. Apparently these speakers have critical mass, so that increasingly new learners of the language (including young native speakers) get more 'incorrect' input of this type than 'correct' input, so that they learn the rule: Even if you mean 1, you have to say 2 instead.
This is a good example of the natural process of language change. It gradually turns grammar mistakes into correct grammar. Maybe one day it will be mandatory to replace 1 by 2. But for now, there is still a large body of classical English literature that consistently uses 1 when the author means 1 and 2 when the author means 2.
But a quick search in a corpus of English literature suggests that the frequency of 1 relative to 2 is actually slowly increasing. I suspect this could be the result of the activities of copy editors, who may be more consistently correcting 2 to 1 nowadays as the number of authors who get this 'wrong' is increasing.
Very thorough explanations! However, I still think that you could also use "He could not have read it" in your first example, such as "He still doesn't know the contents of the book now. He could not have read it." It is the conditional sense for the possibilities.
Here is my example: Tom could go there this weekend, but he would rather hang out with his friends. (He is able to, but he chooses not to.) "Could" is not only used as the past tense of "can".
The first paragraph in Johaquila's reply makes sense and, actually, "He cannot have read this book" is better English and is correct, even if the construction is not familiar. Something else to remember is that "could" is conditional tense and Duolingo may have read "could" as conditional instead of past.
Yes, I totally agree. That's a very good point. Since we are dealing with the modal can in this case, there is the additional complication that could isn't necessarily past tense but can also be interpreted as a softened present tense form of can. I suspect that this is one of the reasons for this change of grammar that is going on at the moment. When people say 1 (i.e. use the present tense variant) but based on could rather than can, others may well think they are actually saying 2, because they are indistinguishable.
Of course, here we are in the special situation that we also have a French version of the sentence, which uses peut (can), not pourrait (could).
Awesome response, @johaquila. Thanks, and I totally agree, even though I originally answered could not have read and was marked wrong (and I am a native American English speaker). There is a distinction even in English between could not have and cannot have, although perhaps subtle and losing this distinction as you say. I think it is important for us learners of French to realize that this distinction remains meaningful in modern French, so it is best that we also learn it and utilize it.
The real point is that the French sentence uses "peut", not "pouvait", and therefore the point of reference is the present, not somewhere in the past:
It is not possible (now, based on today's knowledge) that he has read the book (in the past) by now.
In particular, potential reading events close to the present time are included and are probably the most relevant.
Some English speakers no longer follow the standard Indo-European way of dealing with tenses. They say "could not" instead of "cannot" just because the potential reading happened - or rather didn't happen - in the past, with no regard for when the possibility (which is expressed by can/could) is judged. This started as a clear grammar mistake, but is by now so common that it must be considered correct. But even if we grant that decades of widespread misuse have made it (somewhat) correct, it still has an extra past tense where there could be a present tense, and so it is natural to interpret this new variant with could as reaching further into the past compared to the standard variant with can.
Your perception is incorrect. Modern English is replete with newly constructed tenses which didn't exist 50 years ago. Find me "cannot have read" in a book which wasn't printed since the 70's.
Another example is "we will have read this book." It's just wrong: it's "we would have read this book" because there's no way to escape the hypothetical mood. This is the same thing except in the past tense. Therefore "cannot have read" grates the ear.
If I understand you correctly, you are claiming that the distinction between "cannot have read" and "could not have read" is a recent phenomenon. That's exactly the wrong way round, though if in your idiolect (= personal version of English) only "could not have read" is possible, then it's perfectly natural for you to think this way. See Wikipedia on the recency illusion.
This distinction is made in every European language I know, and in fact English is the only European language I know in which it is arguably not a grammar mistake to say the equivalent of "could not have read" instead of the equivalent of "cannot have read".
You can see on Google's n-gram viewer (URL shortened because the forum software messes with certain complicated links) how the frequency of "cannot have read" as compared to "could not have read" changed in English books over the last 200 years. 200 years ago, "cannot have" was about half as common as "could not have", which makes sense for semantic reasons even though confusing the two constructions in the way many people do today was a rare grammar error at the time. But its popularity decreased over time, and nowadays it's only half as common as it used to be.
But the data is probably distorted because the ratio of literary genres in Google's corpus changed over time. If we set the corpus to "English fiction" and search again, we get a different picture: The two constructions were equally common in fiction in the early 19th century, followed by a rapid decline of "cannot have read" to about a third of the original level until 1860. I would guess that at this point editors became aware that their authors were beginning to erroneously write "could not have" where only "cannot have" made sense and watched out for this problem to correct it. So "cannot have read" became a bit more common again, up to a further decline around 1920. Today it's still at 1920 levels, which is roughly a fifth of the original frequency.
As the fiction data may well be distorted by changing fashions concerning writing style (direct speech vs. indirect speech and similar issues), one should really do some further analysis. But the one thing that is absolutely clear is that "cannot have read" is not a recent phenomenon at all.
If you are still not convinced, here is the third Google books hit I got for "cannot have read":
- When my Honourable and Learned Friend makes that statement, I repeat that he cannot have read this very identical clause to which he is objecting, for it expressly declares that the persons apprenticed under it are to be placed on precisely the same footing as other apprenticed labourers.
That's Edward Stanley (later to become the 14th Earl of Derby and three times Prime Minister of England) arguing for the abolition of slavery in the British Parliament in 1833.
The fifth hit is even a bit earlier (from an 1821 literary journal):
- G.M. illiberally insinuates that one who differs from him in opinion, cannot have read any British poet: he shall find, however, that I have read Byron and Wordsworth; though I confess that I never could get through the latter's "drowsy, frowzy Poem, call'd 'The Excursion.'"
The next hit (for me) is from an 1882 parliamentary debate in New Zealand. And on the second page of hits I find this:
- You must have seen, but you cannot have read, what he has lately published against our Friend and Me.
That's from a letter written by no lesser than Alexander Pope, around 1728.
Interesting. I wrote this intuitively, but I just read that the difference is as follows: less is for amount and lesser is for quality. This is clearly not a full explanation, as some of the examples here show, but I think it's an approximation that often works, and it seems to capture the different nuances in those cases in which both words can be used.
In my idiolect, "written by no less than Alexander Pope" would be borderline correct but bad style. The difference is more marked with "written by no lesser man than Alexander Pope" (correct) vs. "written by no less man than Alexander Pope" (ungrammatical) or "written by no less a man than Alexander Pope" (grammatical, but is likely to be about manliness rather than status).
PS: You are of course just as wrong about "will have read". Like "can[not] have read", this is an example of a perfectly normal construction. The only difference is that for semantic reasons it's much rarer in normal speech and appears primarily in grammar books. Here is a normal example from 1813:
- Cole voluntarily underwent four separate examinations; Bidgood one, and Fanny Lloyd one, all which you will have read in the foregoing Number.
And lest you think the construction is completely antiquated, or that it isn't used in American English, here is one from a 2009 book published in the US (first edition was 1996):
- By plagiarizing a sample essay from this book, you will not only violate federal copyright laws but will also jeopardize your chances for admission to the school of your choice, since many admissions officers will have read this book and will be on the lookout for application essays that resemble the ones herein.
@Da-s We will have read this book is perfectly good English and in a tense that is used all the time. For example, if we are assigned a book at the beginning of a course and will be tested on our knowlwdge of this book at the end of the course, it is assumed that we have not read this book yet (at the start of the course). But we will have read this book by the end of the course and before the exam. There is a name for this tense in English, like the Future Perfect or Future Past... I don't know; maybe someone can enlighten us both. But it refers to an event in the future that will be in the past relevant to another event that is even further out in the future.
The problem with DuoLingo's first translation is that it is not correct in English ("...have have read"). The second option accepted as correct, "He cannot have read this book" is indeed a direct translation into English, but in general, when translating, word-for-word translations don't usually work, and if they do, they are not usually the best option. In this case, "He cannot have read this book" is correct (a direct translation into English), however, in U.S Engish, at least, it is more common to say, "He could not have read this book," which DuoLingo considers incorrect.
The duplication of have has been fixed by now. The problem with "could not have read" instead of "cannot have read" is that it has a different primary meaning and that its generalised use (or abuse) is limited to some variants of English.
It is often a good strategy to learn using one's native language more precisely when learning a foreign language. (Conversely, more precise language use in one's native language is often mentioned as a beneficial side effect of learning a foreign language.)
"...could not have have read.." is obviously just a silly mistake. I wish they'd fix it.
As for "He cannot have read this book", I don't know where you learned your English, but it's perfectly conventional English where I am - western North America.
For example - you are discussing a review of a book you know well. The reviewer criticizes characters that aren't even in the book, events that never took place, etc., and you say, in exasperation, "What is the matter with this reviewer? He cannot have read this book."
I think a lot of people seem not to be aware of epistemic "can"; "he can't have (done X)" = "based on what I know, it's not possible that he has (done X)". Meanwhile "he couldn't have..." = "It wasn't possible that he had" (past) or "it wouldn't have been possible that he had" (conditional).
No, it should not be accepted because you should learn to make the can/could distinction in English as carefully as French speakers do. As it is put in the second answer on this page, cannot is about present impossibility (of having read the book before now) and could not is about impossibility at some point in the past (impossibility of having read the book until that point in the past).
And one should look at a discussion page at least superficially before dropping a comment. About half of the comments on this page are already about this very point.
Can someone explain the rule behind peut avoir lu. I get the negation, so skip that. I realize when you have two verbs following each other, the second typically is in the infinitive form (être sometimes being the exception), and since this is c.p. action lire is in the c.p. form, but why isn't avoir in it's c.p. form (a)? Does être/avoir always stay in their infinitive form in this scenario? If so, is there a rule I can read?
Ahhhh, okay. In English, it is very common to say "He could not have read this book." and sometimes "He cannot have read this book." However, Duolingo pays a whole lot of attention to grammar. "Il ne peut pas" means "He cannot", so Duolingo is justified. "He could not would be "Il ne pourrait pas" or "Il ne pouvait pas", depending on the context and tense...Sorry, this is late and somebody has probably made the discovery, but just for the sake of replying.
Yes, "he could not have read" sounds wrong to me as well as a translation of "il ne peut pas avoir lu". Nevertheless it is (I think) correct, because American English speakers get the tense wrong so often in such cases that it's no longer false.
It is still possible to say "he cannot have read", which is unambiguous. But "he could not have read" can mean both "il ne peut pas avoir lu" and "il ne pouvait pas avoir lu", at least in American English.
It guess it really depends on your variant of English. The English used in this course is often influenced by native French speakers. For the reason a native French speaker might not accept your translation, see my earlier response to AnnaTall. Basically the underlying problem causing the confusion is the tendency of English speakers to conflate all sorts of constructions that expressed different nuances only a few centuries ago (at most).
That's not a plausible interpretation because it would be expressed in French in a much more straightforward way:
- Il ne pouvait pas lire le livre.
The unusual construction in this French sentence is specifically for when the main action (pouvoir) occurs in the present and the dependent action (lire) happened in the past. This is not something that people normally write in error.
The translation of the sentence is definitely "He cannot have read this book." It is correct grammar, but it is still very problematic. We would almost never say such a thing; we would use the word "could." But, if you are trying to learn the conditional tense in French, I believe it's more difficult than the present tense, based on my studies in college many years ago. My French teacher reprimanded me when I tried to use the term "Je peut" (I hope I got the spelling right.) and INSISTED that I was being RUDE UNLESS I said "Je pouvais . . . ." So, I think the rudeness of this sentence needs to be acknowledged, but not altered in translation.
Yes, Johaquita - I DID mean the difference between "veux" and "voudrais" and NOT the corresponding conjugations of the verb "pouvoir." But, if a modal verb is a more polite way of saying something, then it stands to reason that the non-modal verb, present tense or not, is slightly - if not positively - rude.
The difference of mood (not tense) is only relevant to politeness to the extent that the indicative (= normal mood) of the verb expresses something that typically inconveniences someone. And it makes a major difference who is or isn't potentially inconvenienced. In French just like in English, because this is about human nature more than any particular language.
Pouvoir (= can) potentially inconveniences the actor (subject of the verb), and vouloir (= want) potentially inconveniences other people. If I say "I could help you" instead of "I can help you", it's certainly not to be polite. Similarly, saying "I am sure you would like another cup of tea" instead of "I am sure you want another cup of tea" is not really more polite. At least not significantly. But if I say "You could help me" instead of "You can help me", or if I say "I would like another cup of tea" instead of "I want another cup of tea", then it is clearly a much more polite version.
Re: "That is, so many people made this mistake, that a critical mass of children picked it up as correct. "
I'm in my 60s and a native English speaker. It's no longer considered a mistake, and it hasn't been a mistake for many years. English has a sad history from the 19th century of people trying to impose grammatical structures from classical languages. People, including Winston Churchill rebelled against that sort of thing.
Sorry, but nowadays, "He couldn't have read this book" is better English. Put your grammar book away and listen to native speakers.
Let me guess: You are a native American English speaker, right? According to to Google's n-gram viewer, the ratio of "cannot have" to "could not have" is 50 % higher in British English literature compared to American English literature. This seems to support my impression that "cannot have" is alive and well in British English and that the change happened only in American English.
English prescriptivists are guilty of a lot of silly zombie rules like those about 'stranded prepositions' or 'split infinitives', but this is not one of them. In this case, English is actually acquiring a special exception to its grammar that non-native speakers learning American English in school need to practise with drills because it's against the inherent logic of how the tenses work:
- Today he is unable to understand that Caesar was an emperor.
- Yesterday he was unable to understand that Caesar was an emperor.
- Today he cannot understand that Caesar was an emperor
- Yesterday he could not understand that Caesar was an emperor.
- Today she isn't in the position to say that he has read the book.
- Yesterday she wasn't in the position to say that she had read the book.
- She cannot have read the book by today.
- She could not have read the book by yesterday.
Only in the last pair of sentences has it become acceptable (or even required) to replace can by could. This is clearly an irregularity. As I demonstrated with quotations from the 19th century, this irregularity was definitely not obligatory then - if it even existed. I tried to settle this by inspecting Google Books hits from before 1700, but both "cannot have" and "could not have" are so sparse that I was able to look through them all - without finding a single example either way. I also looked at many examples between 1700 and 1800, without success either way. There were no clear examples for "cannot have", and all examples for "could not have" were in hypothetical situations.
Basically I don't know why you're even bothering about any usage before the 21st century. Who cares? It's largely irrelevant to what is a modern colloquial language course.
They probably are irregular uses, but this course is full of irregular phrases in both French and English, some bordering on slang, and so it should be. A lot has changed in both English and French from the time I learned French at school in the 60s.
If we are supposed to be learning a language that is relevant to literature, then we would have covered the past historic tense for one thing.
In any other English than the English of proof-readers, "She couldn't have read the book by yesterday" is perfectly good English. My English teacher in the sixties would have said such a thing.
I'm not American either. I'm an Australian English speaker but I have worked all over the world. My langue de naissance was Scottish Gaelic, but I have largely forgotten how to speak it, although understanding it is almost instinctive.
I bother with these things because I'm a language enthusiast to whom it actually matters how rules of grammar came about.
I'm a bit puzzled by your comment concerning "She couldn't have read the book by yesterday". That's actually what I wrote about above as being totally regular. What is irregular is "She couldn't have read the book by today", when used in a non-hypothetical context. (I.e. with "couldn't" used as past tense for referring to today's state.)
She couldn’t have read the book by today is fine too. If someone is talking about a book and is getting it all mixed up, someone might whisper “he couldn’t have read that book” . He can’t have read that book means the same. I fail to see the distinction between yesterday and today in your example.
English is changing rapidly, partly due to non native speakers. For example “ I look forward to see you tomorrow” .
Mark my words, that will be the correct phrase in as little as ten years time. “ I look forward to seeing you tomorrow “ will have fallen into disuse.
English is probably the most dynamic language in the world today.