It's a little.. peculiar to him, that this creature should seem so interested in his company, for that is really the only way to describe it. He's making conversation, asking him questions as if it's curious, which Castiel finds more than a little puzzling. Why should it want to know him? Why should it care? He can't say that he rightly understands, but there's little enough to be done for it, even if Castiel doesn't particularly feel like conversing. It seems he has little enough choice.

"Of course not, ghosts do not exis-"

He starts, then stops himself, because well, clearly Castiel's assumptions about the world were wrong enough when monsters seem to roam freely in abandoned castles, so he presses his lips tightly together, and starts again.

"No."