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.
(..) we weren't at war with Eastasia at all. It was Eurasia. - The last four years, I think. - Another example. A serious delusion. Photographs about which you've had hallucinations, which you believed you held in your hand. They never existed. Say what you're about to say, Winston. They exist. (..)1984 1984