This has a biological element to it, so I have also asked it on Biology SE, but there is an interesting philosophical element as well. What is it that makes us 'alive'? Our heart beat? Our brain functionality? These questions point to the overall question: what makes someone 'dead'?

  • If you believe the human "soul" can live outside a body, the question might be "when can we declare a human body dead and thus bury/burn it?". People have been declared "dead" by some standard X and then recovered to become alive again, so another question might be "what criteria for death can we use that is irreversible under reasonable circumstances?" – barrycarter Nov 8 '17 at 14:11
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    I think that this question might be a duplicate on this site and therefore might be closed. But either way, this is a very interesting topic that has a lot of discussion in philosophy because it touches on myriad things such as the nature of existence, personal identity, the philosophy of mind, etc. The Stanford Encyclopedia of Philosophy has two great articles, one that is pretty much exactly on this topic, The Definition of Death and one on death, Death. – Not_Here Nov 8 '17 at 15:22
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    This topic is a massive one. There's probably thousands of volumes on the topic, each with an opinion which is inconsistent with the last. One approach I have found very useful for trying to pick away at them is to ask "what does it mean to be 'dead' to you?" I mean that in the sense of "If I could tell you authoritatively that some particular thing was dead, how would that affect your thoughts and actions?" Dead is a difficult word because it's a very powerful loaded concept, and different people load it in different ways. – Cort Ammon Nov 8 '17 at 15:29
  • @Not_Here those articles contain the information I was seeking and therefore, in my mind, answer my question. Thank you! – J. Tate Nov 8 '17 at 15:38

The standard, biological definition. Living things:

  1. Are composed of cells
  2. Have different levels of cellular organization
  3. Use energy
  4. Respond to their environment
  5. Grow
  6. Reproduce
  7. Adapt to their environment

While it's not entirely clear whether certain organic molecules (like virii) meet all of these criteria, it's agreed that the overwhelming number of living things share these criteria.

The clinical definition of being dead is:


While looking at the 'philosophical' question of whether or not someone is dead might sound interesting, I think what you're actually interested in knowing is under what conditions someone is no longer a conscious person.

Being 'dead' has a very real, and straight-forward answer. Once you die your body will no longer work. If you aren't dead, but unconscious, it is possible that your consciousness can be restored with the right types of therapy.

Lacking consciousness would be caused by very specific conditions in the brain.

Anyway, hope that helps.


The definition of alive is often given as "not dead". Ironically, the definition of dead is often given as "not alive". I got those from a online definition search. Biologist struggle to define those things that are alive. Though most would agree that a squirrel is alive, there is some debate about a virus and a prion really pushes the envelope. The best definition I have found for what is alive is an entity that can acquire "food", metabolize and act. I put food in quotes on food as it may not be what you expect. Plants "eats" sunlight for instance. Given that definition a Human is dead when they can no longer do those things.

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