no one could have known/could know

[floyd6]

A
1. No one could have known...
2. No one could know...

B
1. ...what I thought.
2. ...what I had thought.

A + B


Which is correct and why? THANK YOU.

 

[Raymott]

A
1. No one could have known...
2. No one could know...

B
1. ...what I thought.
2. ...what I had thought.

A + B

Which is correct and why? THANK YOU.

A1 + B1
A1 + B2
A2 + B1
A2 + B2
They are all possible. Why? Because none of these combinations produces an ungrammatical sentence.

If you intend to ask what the difference is, you could try to answer that first.

 

[floyd6]

What is the difference then?

 

[Raymott]

What is the difference then?

Did you read my post?

 

[Mr. X]

What is the difference then?

No one could know what I (had) thought.

Could could mean past tense of can, in which case it'd be: no one was able to know...
Or, could could also mean: would be able to. No one would be able to know...

However, no one could have known... this could only mean: no one would have been able to know...

Disclaimer: I am not a teacher, so...:-(

 

[floyd6]

we're talking about the past here, so either form is correct, right?

 

[greegorush]

Raymott, can you explain why all combinations are possible?

As I know "could" can be used in the past describing someone's abilities. Otherwise, we have to use "could have".

So, my sentences would be:
A1+B1
A1+B2

An explanation is urgently required!

 

[Raymott]

Raymott, can you explain why all combinations are possible?

As I know "could" can be used in the past describing someone's abilities. Otherwise, we have to use "could have".

So, my sentences would be:
A1+B1
A1+B2

An explanation is urgently required!

A2 can be used in the present tense, with 'could' the present conditional of can. I'll explain further with examples etc. once floyd6 gives his understanding of the four sentences as I asked, or delegates it someone else. Perhaps you could explain what you think they mean?

What's the urgency?

 

[jiamajia]

1. No one could have known...

Something has happaned. Before that, nobody knew that it would happen. Now you could say: no one could have known it would happen.




2. No one could know...
Do you know if there will be a traffic accident at the intersection of 33rd street and 6th avenue tomorrow? You don't, I don't and nobody does. You could say: nobody could know.

 

[Raymott]

1. No one could have known...

Something has happaned. Before that, nobody knew that it would happen.
In fact, not only did nobody know it would happen; it was impossible for anyone to know; at that time nobody could know.
Now you could say: no one could have known it would happen.

Yes, that explains A1+B1.
No one could have known it would happen.
No one could have known that I thought that.
No one could have known what I thought.
Let's say the "something" that happened was that I told them what I thought; that's the "before" clause - the recent event in the past:
No one could have known what I thought before I told them.

Timeline: a) I thought something -> b) I told them what I thought -> c) They knew what I thought.
The topic sentence says that c) could not happen before b).

Another variant is: "Nobody could have known what I was thinking." in which a) in the timeline is "I was thinking something".


2. No one could know...
Do you know if there will be a traffic accident at the intersection of 33rd street and 6th avenue tomorrow? You don't, I don't and nobody does. You could say: nobody could know
Nobody could know that that would happen.
Nobody could know that an accident will happen.
Nobody could know what I will think.
A2+B1 is of the form: Nobody could know what I did think (what I thought).
That is, the second clause in your example refers to the future, rather than the past, which was the question. So 'could' in your example functions as the conditional of 'can', not the past tense of 'can'.

In A2+B1, "Nobody could know what I thought" you can't tell if the "could" is past tense or present conditional. It can mean either of:
i) It would be impossible for anyone to know [now] what I thought [then ]. (pres. cond.)
ii) It was impossible for anyone to know [then] what I thought [then]. (past. cond)

That leaves A1+B2, A2+B2. Anyone want to try for a meaning of these?

 

[greegorush]

Thank you, Raymott. I made my mind up concerning the "could" rules so I thought I missed something, so I wanted to know it as soon as possible.

Returning to your questions:

1. No one could have known what I had thought.
It is a past conditional sentence.

2. No one could know what I had thought.
This sentence means that it's impossible that somebody knows what I thought 10 minutes ago; yesterday...

 

[Raymott]

Thank you, Raymott. I made my mind up concerning the "could" rules so I thought I missed something, so I wanted to know it as soon as possible.

Returning to your questions:

1. No one could have known what I had thought.
It is a past conditional sentence.
That's true, but they all could be, assuming that 'could' refers to the past as well as being conditional.

2. No one could know what I had thought.
This sentence means that it's impossible that somebody knows what I thought 10 minutes ago; yesterday...

These last two are similar to the ones explained above, so an extensive explanation isn't necessary.
The only difference is that the second clause is in the past perfect.
So what is being referred to (what I [had] thought) has to be one step back in the timeline from something else.

A: I know what you thought yesterday. (Simple past of thought)
B: No. Nobody could know [now] what I thought [yesterday].

A: OK, I don't know what you thought yesterday, but I know what you had thought before that.
B: No. Nobody could know [now] what I had thought [before I thought something different yesterday].

A: Well, I could have known what you thought [yesterday].
B: You could have if I told you. But I didn't. Nobody could have known.

etc ...
The context is important as usual. And often either form will work. The subtle differences are not worth getting too worried about.
In principle, each clause in the two-clause sentence will follow the rules for the correct use of tenses for that clause, independently of the other clause.
If the knowing or thinking calls for the present or past or past perfect, that is what should generally be used. But tenses are often simplified in practice.

When A says: "I could have known what you had thought", in real life, he's just as likely to say, "Maybe I knew what you thought?", with the rest of the grammar filled in with adverbs and context.

 

[greegorush]

Thank you for the exhaustive explanation.