What is the correct usage of phrase you don't know what you don't know? Can it be used in formal conversation/writing? I saw this sentence in the book 1q84:
Also explain the difference between the two, thanks. Please let me know as soon as you figure it out. In the first sentence, it seems to me that to know expresses that the speaker experienced the problem/difficulty.
Recently one of my friends told me that there is distinct difference between 'know of something' and 'know about something' expressions. Alright, well, for example, like on saturdays, y’know, what i liked to do. You would use the present perfect to express something that happened previously, without specifying the time. It's not just you that don't know.
Why would you have a problem with this? 'know of' is used when you have personal. In (2), however, the object of. I know how to drive a car.
I know (about) this difficulty/problem. Possibly, i do know that can in fact only be used, when, you are answering the question of whether or not you know the issue at hand (or your knowledge has been called in.