He could not tell if what he was seeing was real or if it was a 'hallucination'.
He has been having 'hallucinations' due to the medication.
(..) Be brave. This isn't real. It's all right, it's all right. You okay? How long do you think you were in the hallucination, Tris? - Twenty minutes? - Three. Four times faster than the average. I've never seen anyone (..)2014 Divergent
(..) I'm going to inject you with a serum that stimulates the part of your brain that processes fear. Great. It induces a hallucination, and then transmitters in the serum allow me to see the images in your mind. You can see inside my mind? Mmm-hmm. (..)2014 Divergent
(..) If I'm unhappy, I'll move back. But for the time being, yes. W...W...With who?... With who, Gil? - No one, I... - One of your crazy hallucinatory friends? I mean, Mom's right about you. You have this part missing. Yeah, I said that first. Anyone whose protagonist makes a living (..)2011 Midnight in Paris