Science deals with objective matters that can be observed, tested, and measured by someone else. An NDE is a subjective experience: It can be felt and reported only by the person who has it. For this and other reasons, some people claim that the NDE cannot be scientifically "real." Conversely, other scientists consider NDEs as scientifically valid as any other intense personal experience. The difference may be that some scientists demand physical proof of reality, while others are less troubled by ambiguity. In any event, tens of thousands of NDEs are being reported from all parts of the world. Something does seem to be happening, whether or not everyone agrees that it is scientifically understandable.