It's hazy – just a series of impressions. (2.1)
If Adam's memories are only a series of impressions – meaning nothing is really specific or particular – is it possible for him to truly know what happened to him in the past? If not, can we really consider his past a reality?
Anyway, he was feeling much better, and he didn't even care if feeling better was only an illusion. (8.2)
Here Paul's different versions of reality work to his advantage, helping him feel better. Just picture yourself relaxing in your favorite tranquil spot and you'll see what we mean.
He had two birth certificates, two birthdays. Crazily, he thought, Was I born twice? (12.7)
Adam's world has been turned upside down to the point that he actually
wonders whether he was born twice. He can no longer trust the reality he
once knew, so nothing is too odd to be possible.