He says Mary was ill. Let us suppose

we have such a sentence. Let us suppose I have such a sentence: I know John was right.

How can I use the sentence “Visual past”? Is it correct?

Why did John say Marry fell ill?

What is a Can and A Must?

And also I am curious about might in the past, that is may, but with less certainty. That is might have been in the present expresses lesser probability in the present expresses less probability than may. If any, the statement will do in detail. Is it possible to convey subtlety, and why?

What is the meaning behind the word “All the People”?