There are such living-symptoms in brain death as looking well, maintaining the body heart, and sweating etc., because blood can circulate through the body by respirator's moving the heart. Therefore brain death is characterized as 'invisible one' which is unknown about the moment when a person died. Judging from these living-symptoms, patients whose brain are dead will appear to be alive. This appearance depends on the viewpoint from which brain-dead patients are looked on. The viewpoint, which itself is influenced by an interpretation to be changed, has an influence on the way of treatment. Just as those to whom a kitty appears lovely will treat it with love, so those to whom brain-dead patients appear to be alive will treat them as the living. The converse is also possible. Those to whom brain-dead patients appear to be dead will be insensitive to treat them as corpses. Such insensitivity might make it possible to treat even patients of persistent vegetative state as corpses. It suggests the possibility of such 'a slippery slope' as we must not approve only B but C, D, if we approve A so that we cannot help reaching to the end. Now, brain-dead patients appear to be alive if being looked on by their family or friends, but they appear to be dead if by doctors or nurses. What makes the difference between this appearance and that appearance? It depends on what relation people have with patients, namely, whether people regard them as 'it' or 'you'. The relation of 'I-you' is, according to M. Buber, the relation that 'I' stand face to face with 'you'. So long as the brain-dead patients are looked on as 'you', they must appear to be alive.