Chapter 1: Understanding Cryonics

Throughout history, the definition of death has evolved alongside medical progress. Only a few generations ago, a heart attack was considered the absolute end of life because no treatment existed to restart the heart. The development of cardiopulmonary resuscitation (CPR), defibrillation, and artificial ventilation changed this completely. What was once seen as irreversible became reversible through new technology. This ongoing shift has shown that death is not a fixed moment but a process that can, at least in part, be delayed or even reversed.

Modern medicine distinguishes between different stages of death. Clinical death occurs when breathing and blood circulation stop. At this point, tissues remain alive for several minutes, and revival is often possible through CPR. Legal death is the formal declaration made by a physician when life functions have ceased based on current medical standards. Biological death follows when cells begin to break down and tissues lose structure, marking the onset of decay.

Cryonics adds another perspective: the information-theoretical definition of death. According to this concept, a person is only truly dead when the information that encodes their identity, memories, and personality within the brain has been destroyed beyond potential recovery. As long as that information remains physically preserved, the person could, in theory, be restored in the future once science develops the tools to repair and revive damaged tissue.

In practice, cryonics operates within this “window” between legal death and information-theoretical death. Immediately after legal death is declared, specialized teams begin the cryopreservation process. The body is cooled and perfused with protective substances that replace blood and prevent ice formation. This intervention stabilizes cellular structures and preserves the intricate architecture of the brain.

The concept is illustrated in the graph below, known as the cryonics window. It shows the stages from life to death and where cryopreservation fits within that process. The earlier the procedure begins after legal death, the higher the quality of preservation and the greater the chance of future revival. Ideally, cryopreservation would start right after clinical death, when all biological structures are still intact. However, current laws require the declaration of legal death before any procedure can begin. This creates a small but crucial delay in which preservation quality gradually decreases. Once the process of biological decay advances too far and the informational structure of the brain is lost, a person reaches the point of information-theoretical death, beyond which recovery is no longer possible in principle.

Understanding death in these terms changes how cryonics is viewed. It shifts the focus from the immediate loss of vital signs to the preservation of information. By intervening within the cryonics window, the procedure aims to maintain the physical and informational continuity of the person until future medical technology can restore what today remains out of reach.