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?