Subjects could not know they had undergone a PCE if the experience were truly empty of all conceptual content (Bagger 1999, 102–103) since there would be nothing to observe while it is going on, and hence nothing to retain later. Nor could a subject surmise that a PCE had transpired by remembering a “before” and an “after” with an unaccounted for middle. This would fail to distinguish a PCE from plain unconsciousness.