In
Perelandra, Ransom "described us as being in a state of siege, as being, in fact, an enemy-occupied territory, held down by eldils who were at war both with us and with the eldils of "Deep Heaven," or "space."" This is the exact same term that Lewis used in
Mere Christianity when he said, ""Enemy-occupied territory—that is what this world is." :)
Of the fallen eldila - "Oh, they'll put all sorts of things into your head if you let them," said Ransom lightly. "The best plan is to take no notice and keep straight on. Don't try to answer them. They like drawing you into an interminable argument." This is both like and unlike the devils of
The Screwtape Letters. Screwtape advised Wormwood that their best work was sometimes done keeping things out rather than putting things into the heads of mortals. However, I feel that there is still a similarity between the tempting eldila and the devils.
"If you mean, Does my reason accept the view that he will (accidents apart) deliver me safe on the surface of Perelandra? - the answer is Yes," said Ransom. "If you mean, Do my nerves and my imagination respond to this view? - I'm afraid the answer is No. One can believe is anesthetics and yet feel in a panic when they actually put the mask over your face. I think I feel as a man who believes in the future life feels when he is taken out to face a firing party. Perhaps it's good practice." This is very much like what Lewis said in
Mere Christianity -
"Faith... is the art of holding on to things your reason has once accepted, in spite of your changing moods."