I don’t know what happens when we die. Nobody does, I guess except maybe people who are dead. I lost two friends this year, which only mildly intensified my already frequent pondering about life and death.

My hope is that this post will end up supporting a theme about the use, or misuse, of science in forming beliefs about things that aren’t testable using science, but for now, it’s going to focus on death, because a good uplifting topic is just what I need right now (maybe not as much as a good established sarcastic font, that would be life changing).

What do we know about death? We know, with some confidence, that every human being who has lived or is living, has died or will die. That is not in dispute. We have a pretty good way of defining death in humans, but this isn’t perfect. Generally speaking, we say that death, legally, occurs at the irreversible cessation of all functions of the brain. This gets a little tricky, because determining if it’s irreversible isn’t always easy. Determining loss of brain function used to be the hard part, and we used respiration and circulation, but measuring brain function is now relatively easy, it’s just that irreversible part that remains as a sticking point for some, but this is generally because people confuse being brain dead with being in a coma. When we call a patient “brain dead,” it means that all brain function has stopped. Reflexes that require the brainstem are gone, and there is no chance of recovery. This is quite different from a coma in which the patient has some reflexes intact and can usually breathe without a ventilator.

What we don’t know is what happens, subjectively, at that point. We hear stories of people who have “died” and come back. We hear stories of near death experiences. People who experience what feels like they have left their body and moved toward some afterlife experience. I do not doubt these experiences. They clearly happen. To tell somebody that they didn’t experience something is the same as calling them a liar, and I don’t think that’s fair. I do, however, think it’s fair to say that their experience, no matter how compelling, does not provide proof of an afterlife. At the same time, there is nothing that I can say or demonstrate that would provide proof that an afterlife doesn’t exist. This is simply not something that we can test, because it is not a falsifiable hypothesis.

That two-word phrase, falsifiable hypothesis, is so critically important in trying to figure out if something is science or something else. The lack of that falsifiable hypothesis is what lets you know that your question is not in the realm of science, but belongs wholly to philosophy, religion, or some other way of gathering information about the world that is not necessarily weaker than science, but is undoubtedly more flexible than science. My earlier post about life, and when life begins, is a nice example. The when-does-life-begin question isn’t falsifiable because we don’t have a good definition to test. An even better, perhaps less emotionally charged (where’s that sarcastic font?), example is God. God exists. God does not exist. These are two possibilities. The problem is that neither statement can be scientifically rejected. There is simply no way to prove that God doesn’t exist (scientific explanations of things that are attributed to God is not proof of the non-existence of God, because there is no way to prove that God did not create the system in which those explanations were discovered). Likewise, there is simply no way to prove that God exists. There are unexplained phenomena, but that does not prove the existence of God, it simply shows that we don’t understand something. Something that we may, perhaps, understand in the future. The existence of God, therefore, is not a scientific question, but one that belongs in a different realm. Something that is outside the bounds of science. That doesn’t mean that we can’t apply science to some related questions: do the brains of people who believe in God look or work differently from brains of people who do not? Does belief in God make somebody more likely to behave a certain way? Lots of those questions are within the realm of science, but the fundamental question of the existence or inexistence of God is simply not something that is provable, at least not today.

The same is true for the question of what happens after we die. We don’t know because nobody has ever really been dead and come back to life according to our definition of death. An irreversible cessation of all functions of the brain. Irreversible. By definition, if the cessation is reversible, it is not death. This may sound like a silly semantic argument, but there’s a critical factor here. If the brain is not irreversibly non-functional, there is still some function remaining. More importantly, there is a restoration of function, the person comes back to life. Even if we remove “irreversible” from the definition, and allow the possibility that somebody died and came back to life, the brain ceased to function, but then returned to normal function, that moment of return, that split second during which the cortex became active again, holds all that we need to account for every single part of the subjective near-death experience.

Those who consider near-death experiences as proof of an afterlife ignore on critical thing: that time in our memories, time in our dreams, time in our subjective experiences, is not always the same as time in our waking lives. We know this to be true. We have all had dreams that seemed to last for a long time, but we know that the period of sleep associated with dreams generally lasts minutes, sometimes as long as an hour. I’ve certainly had dreams that lasted for longer than an hour of dreamtime, but the whole memory of that long dream, sometimes days long, was all within minutes of non-dream time.

The idea that a near-death experience that lasts for days or weeks requires us to be “dead” (or nearly dead) for the same amount of time is based on a very flawed assumption of how we perceive time in consciousness and unconsciousness. I can live a lifetime in a 5-minute period of REM sleep. Who is to say that I can have the same experience in a split second of restoring brain activity? This, however, is the crux of the argument of a book written not too long ago called “Proof of Heaven: A Neurosurgeon’s Journey into the Afterlife.” The author, a neurosurgeon, is a pseudoscientist, not a scientist, but he gets attention, and people assume he is credible because he’s a doctor. Unfortunately, he’s not the kind of doctor who is required to have training in the scientific method, or how to discern “proof” from conjuncture. This is the kind of thing that hurts science. A non-scientist pretends to be a scientist, says all kinds of things that might be popular with some people, then real scientists point out the flaws, and it creates a false choice: hold on to your core belief and reject science, or accept the science and reject your core belief. For many of us, that’s a no-brainer; some clearly reject the science that they have been rejecting for so long, and others don’t have any problems rejecting core beliefs because we rely on science to form core beliefs. Either way, it’s a false choice because some things are not addressable by science. Beliefs can happen in a non-falsifiable way. The problem is when we create a core belief that is falsifiable, but refuse to budge when it’s falsified. The answer to that problem, make sure that our beliefs are not falsifiable and we’re all set. But Dr. Alexander didn’t do that. Dr. Alexander has a core belief that Heaven and an afterlife exist. Dr. Alexander has a near-death experience that is vivid and lasts for a long time, longer than the period that he was “dead.” Dr. Alexander claims to have the credentials to understand the science of death because he is a neurosurgeon, so his story is considered credible and he sells books. One copy, probably many more, was purchased by a very religious person to be given to a very non-religious person, presumably in a very kind attempt to appeal to that non-religious person’s love of science. That was a kind gesture, but it doesn’t change the fact that Dr. Alexander’s whole argument, that his vivid and long subjective experience is “proof” of an afterlife, is based on a flawed assumption: that time is the same in a subjective dream-like state as it is in awake life. Take that assumption (which we know is not true because we all have likely experienced dreams that lasted much longer than the REM episodes during which they most likely took place.

How do I know that my assumptions are sound? Well, because of the scientific process. My argument is two-fold: dreams occur during REM sleep and the duration of the REM episode is not the same as the duration of the dream. In turn: dreams occur during REM sleep. This is partly true. Dreams can occur outside of REM sleep, but the majority of dreams are thought to occur during REM sleep, and dreaming during REM sleep is reportedly more vivid and memorable. We know this from decades of work in laboratories that study sleep and dreaming. The second point, the duration of the REM episode is not necessarily the same as the duration of the dream. We actually do not need information collected systematically for this: many of us have have taken short naps during which we had long dreams. Even while awake, our perception of time is flexible. “A watched pot doesn’t boil” is based in subjective experience. It really does seem to take longer for the water to boil if we’re paying attention to it, but it seems to boil much faster if we aren’t. Of course, the water boils at the same rate, but our perception of the time it takes is altered by our experience. Taking these things together, it seems more parsimonious to conclude that the afterlife experience that Dr. Alexander reports was more like a dream than anything else. And having a dream is not “proof” of any kind of afterlife. On the other hand, this also does not disprove an afterlife, it just means that there is an alternative explanation for what Dr. Alexander experienced, which means it is not proof of anything.

So I’m left with no real information about what happens after we die. Which is both comforting and frightening.