Harry had never even imagined such a strange and splendid place. It was lit by thousands and thousands of candles that were floating in midair over four long tables, where the rest of the students were sitting. These tables were laid with glittering golden plates and goblets. At the top of the hall was another long table where the teachers were sitting. Professor McGonagall led the first years up here, so that they came to a halt in a line facing the other students, with the teachers behind them. The hundreds of faces staring at them looked like pale lanterns in the flickering candlelight. Dotted here and there among the students, the ghosts shone misty silver. Mainly to avoid all the staring eyes, Harry looked upward and saw a velvety black ceiling dotted with stars. He heard
Hermione whisper, "It's bewitched to look like the sky outside. I read about it in Hogwarts, A History." It was hard to believe there was a ceiling there at all, and that the Great Hall didn't simply open on to the heavens.
(Harry Potter and the Sorcerer's Stone)
Before reading on RHD that simply is posed before a negative when whose meaning is absolutely, I thought simply is the different expression of at all, which is in the same sentence. In my eye, ‘the Great Hall didn’t open on to the heavens at all’ is natural in the context. Doe it not have the meaning and have the sense of just/only, simply not being posed before a negative?
