What does "book" and "sell" mean here, following the article's excellent explanation on how those terms vary wildly. Are those figures per year or lifetime for the books?
To be fair to JP, he's not always right but in this instance, he does have a point.
I believe in physics but I also believe that the map is not the territory. Go back a few centuries and the model of the atom was that of the Christmas pudding. We now know better but our own models are most certainly not correct. Thus I'm believing in something I know to be faulty on some level.
Similarly with God, each religion's conception is different. If you believe in a pagan religion you believe in lots of different gods. If you believe in a monotheistic religion you believe in one God.
It's very difficult to have a conversation free of misunderstanding on abstract matters unless you have a good grasp of the underlying concepts your conversational partner embodies in a word and vice versa. With a subject as touchy as religion, it's prudent to define terms early.
Likewise, I think asking for definitions of 'book' and 'sold' are perfectly valid questions.