At the end of Listen, I got the feeling they wanted to write it off as an illusion of the Doctor, since Clara grabbed his ankle when he was a kid. So because of this there are no beings which perfected hiding, they just do not exist. Is this what they were going for? is it open to our own interpretation? or are there actually beings which have perfected hiding?
It just isn't really clear to me.
To me, those beings do exist since we saw the Doctor placing the chalk on the book where as it wasn't there anymore when he wanted to pick it up and listen was written on the board. We did not see the Doctor do it and the camera was on him the whole time right?
On a side note I was really on edge when I saw LISTEN on the board. A week long I humored my self thinking they might be real.