The purpose of cryonics is to save the lives of living people, not inter the bodies of dead people. Death is a neurological process that begins after the heart stops. A stopped heart only causes death if nothing is done when the heart stops. Cryonics proposes to do something. In the words of a mainstream critical care expert writing for the American College of Surgeons, “In this era of critical care, death is more a process than an event…. A prognosis of death…cannot serve as a diagnosis.”
Alcor uses life support equipment to restore blood circulation to maintain brain viability after the heart stops, ideally within minutes. This means that every cell and tissue of a cryonics patient can be just as alive at the beginning of cryonics procedures as any other medical patient. Care of a terminally-ill patient can legally be transferred to Alcor as soon as the heart stops beating. Legal death declared at that moment is simply a certification that there’s nothing more contemporary medicine can do for a dying patient.
Dying is a process, not an event. The purpose of cryonics is to intercept and stop this dying process within the window of time that it may be reversible in the future. The first few minutes of clinical death are certainly reversible, even today. There are good reasons to believe that this window will extend further in the future. That is why cryonics is sometimes implemented even long after the heart stops. Cryonics is not a belief that the dead can be revived. Cryonics is a belief that no one is really dead until the information content of the brain is lost, and that low temperatures can prevent this loss.
The cryopreservation phase of cryonics will not be reversible for a very long time. But this still does not mean cryonics patients are dead. Life can be stopped and restarted under the right conditions, and life is often mistaken for death when resuscitation methods are not sufficiently advanced. If cryonics patients are ever successfully recovered, they will not have been dead by definition. They will have been unconscious, not dead. Saying cryonics cannot work because cryonics patients are dead is a circular argument. The statement assumes the conclusion it claims to prove!