to be ignorant/unconscious/unaware of something; to be in the dark about something; not to know
He doesn't know the way back home
I know nothing about his past; I don't know anything about his past
He's unaware that I'm ill today
We are not unaware of her difficulties
Unknown to his wife and children, he sold the house; He sold the house without his wife and children's knowledge
The boy doesn't know what it is to be hungry; The boy knows no hunger; The boy doesn't know the meaning of hunger
cannot
He cannot swim/ride a bicycle
They could do nothing except pray
to be insensitive/insensible/numb to something
This blind man is insensitive to pain/cold; This blind man is insensible to pain/cold
impervious
To be dead/impervious to reason