"It appears that the devastation we brought upon ourselves was complete; Heaven, Hell and Purgatory were atomized as well. So when a soul leaves the body it has nowhere to go, and must remain here, in the Metro. A harsh, but not undeserved atonement for our sins, wouldn't you agree?"
"Wicked phenomenon, yes? But, you know, it’s not any more "evil" than, say… fire. It all depends on your point of view. Try to get a better understanding of things before you make your judgement. Let's move out now, it's not safe here." (This quote can be also heard during the end of the Black Station level, if you choose the Dark Ones Side).
"Keeping silent? You are turning into a Ranger. Take a close look at the road you follow, Artyom. And be aware of how it might end."
Listen to that quote:
"You reap what you sow, Artyom. Force answers force, war breeds war, and death only brings death. To break this vicious circle one must do more than just act without any thought or doubt." (This quote also can be heard before the good ending after escaping the attacks from the dark ones.)