Is/Was

Both are possible, depending on the context.

I didn't know Jack is such a good person.
e.g.
[Jack is a good person.] Stating an opinion/fact.

I didn't know Jack was such a good person.
e.g.
[Jack is dead.] or
[Jack is not a good person anymore.]

I disagree -- I think you can certainly say "I didn't know Jack was such a good person" even if Jack is alive and well and still good. In fact, I think it's preferable to "I didn't know Jack is such a good person" -- but I'm afraid I don't have the grammar vocabulary to explain why. CJ? anyone else?

khoffI disagree -- I think you can certainly say "I didn't know Jack was such a good person" even if Jack is alive and well and still good. In fact, I think it's preferable to "I didn't know Jack is such a good person"

I agree that "I didn't know Jack was such a good person" doesn't imply that he is dead. However, "I didn't know Jack is such a good person" wou

khoffI disagree

I meant the above as examples; not as exclusive explanations. I see that I should have put the "e.g." below the sentences I wrote.

Edit: all fixed up now!

vkr6078 I didn't know he was/is such a good person.Which is correct in the above sentence. Is/was and why ?

If you want to play it safe, always use the past tense after these expressions (below) because the past tense is always correct. (Plus, you won't have to consider extraneous ideas like whether someone is alive or dead, whether facts are still true, or w

Thank you all! I am even more confused now. It seems even you people are not sure. Forget about how native speakers say. Let's get back to grammar. Which is grammatically correct ?

vkr6078Forget about how native speakers say

Descriptive grammar is based on evidence - how contemporary native speakers use the language.
Prescriptive grammar attempts to set a single unchanging standard defining exact rights and wrongs of usage.

Educators and professional have largely discarded prescriptive grammar. Languages change and evolve; s

vkr6078Which is grammatically correct?

Both are grammatically correct. Being grammatically correct is easy. You've already jumped that low hurdle. But once you know a couple of ways to say things that are grammatically correct, it's time to move on to choosing things that sound right to native speakers. That's a

vkr6078 It seems even you people are not sure.

We are sure. We may occasionally not express ourselves as clearly as we might, but none of us has any serious doubts about this. CJ is more likely to backshift than I when it is not essential, but that is just personal preference.

Thank you guys! I am relatively good at grammar but think too much about it. Probably that's why I often confuse which is correct and which is not. It's more of a confusion rather than not knowing. Again thank you very much for your answers. I want to have very fluency in this language. I have been learning new vocabulary for the last few weeks. The problem for me is I can't speak in English fluen