I’ve discussed before how one of the consolations offered by many religions is the possibility of an afterlife. That after death you’ll have some real quality time with the guy (typically referred to in the male sense in Abrahamic religions anyway) you’ve been worshiping and be able to get reunited with all your loved ones (assuming you guessed the correct religion of course, which may not always be necessary for all religions). This state of affairs is often said to last for eternity.
I’ve seen comments from many of my fellow atheists elsewhere that living for eternity would be horrible. After doing everything you could every possibly want, what could possibly keep one interested in anything anymore after the first 50 billion years or so? A typical analogy is that of an eagle whose wing tip brushes off one grain of sand each day from a large mountain. Starting from the first day to when the disappearance of the mountain is like one day of eternity. Sounds like my commute to work. In fact, the situation is worse. Since eternity is, by definition, unbounded, the time for the mountain’s disappearance might as well count for a fraction of a second of eternity.
That being said, I don’t really mind the idea of having eternal life. But if I were designing an Eternal Life Package, I would probably include an opt out clause that would allow the eternal life participant to painlessly blink oneself out of existence when one has had enough. There are, after all, some interesting events to observe in the future. When the sun expands to engulf the current orbit of the earth in 3-5 billion years, it would be kind of cool to see the land melt and watch the planet possibly burn up. If you had any bets on that, that would be the time to collect. Although I hope our descendants will have figured out how to save the biosphere first. Speaking of descendants, it would be interesting to see what path evolution takes in regards to our species and others.
But let’s get back to reality.
Is there an afterlife as many religions claim? For it have any meaning, it should mean that your conscious identity continues to exist after your body dies. That your personality and memory continues to exist, that you continue to have thoughts, and are probably able to make decisions and observations. The fact that personality and memory are inexorably linked to the physical brain has been discussed in great detail elsewhere. I shall not repeat all that discussion here, except to say that this indeed makes the case for an existence of the self independent of the body extraordinarily weak. One is strongly tempted to simply close the case right there. Advances in neuroscience continue to make this case stronger. One would think that religious fundamentalists would be putting more effort into supporting dualism. As it is, while fundamentalist efforts seem directed towards fighting the realities of evolution, they haven’t noticed their souls have been taken away.
But if one could brush aside those arguments, is there anything else that may provide evidence for an afterlife? In fact, many propose just such evidence in the form of near death experiences (NDEs). So, let’s take a look at these. If one looks at near death experience websites, such as NearDeath.com, one might be tempted to conclude that the evidence for life after death is pretty strong. There certainly a lot of cases presented, and they even purport to show scientific evidence in support of life after death. I certainly won’t deny that people who have had a near death experience have had a real experience. The question boils down to interpretation. Is life after death necessary to explain these experiences? If a natural materialistic explanation can be shown to be a likely cause, then it seems reasonable to conclude that the life after death hypothesis is not necessary. One could try to go through each case presented above and try to poke holes, but for the purpose of this general discussion, that would probably not be very instructive. Nor is all the information available for each case necessary to do a full analysis. Certainly during these moments the doctors and nurses are presented with the more immediate urgency of saving a life rather than doing careful controls. What we can try to do is isolate out what seem to be some of the common features in these experiences to see if a materialistic explanation suffices.
There are some experiences common to many, but not all, of near death experiences. Some of these have been outlined here. They include such things as out of body experiences, a tunnel (not on the list, but it is an element I’ve read about in several of these stories), a bright “loving” light, and a life review. One thing to keep in mind in this discussion is that we do not directly experience reality. Information is brought in from our senses and used by the brain to construct a model of reality.
Let’s start with the life review. Typically, this is described as a nonjudgmental replay of everything that has gone in ones life. It turns out that a fellow by the name of Stephen Thaler reproduced this effect using artificial neural networks. By changing the weights between connections, effectively killing off neurons, he was able to observe the network reliving its past life. From the link:
So after work, Thaler went home and created the epitome of a killer application – a computer program he called the Grim Reaper. The reaper dismantles neural networks by changing its connection weights. It is the biological equivalent of killing neurons. Pick off enough neurons, and the result is death.
On Christmas Eve 1989, Thaler typed the lyrics to some of his favorite Christmas carols into a neural network. Once he’d taught the network the songs, he unleashed the Grim Reaper. As the reaper slashed away connections, the network’s digital life began to flash before its eyes. The program randomly spit out perfectly remembered carols as the killer application severed the first connections. But as its wounds grew deeper, and the network faded toward black, it began to hallucinate.
The network wove its remaining strands of memory together, producing what someone else might interpret as damaged memories, but what Thaler recognized as new ideas. In its death spiral, the program dreamed up new carols, each created from shards of its shattered memories.
“Its last dying gasp was, ‘All men go to good earth in one eternal silent night,'” Thaler said.
Although the human brain is more complex, it looks like one of the properties of a dying neural network is exactly what would be perceived as a life review. In addition, we also get the creation of new experiences as the brain or network seems to keep or put together some model of reality. This may explain some of the elaborate stories we sometimes see associated with NDEs. So this, at least, evidently can be explained in materialistic terms.
What about those out of body experiences (OBEs) though? Surely that is evidence for a soul hovering above the body watching events. In fact, this phenomena has been widely discussed and reproduced. A 2005 article in the Journal of Neuroscience indicates that the temporoparietal junction in the brain is responsible for the sense of unity with the body and its failure may result in OBEs. More discussion on OBEs can be found at the wiki of course. It is noted there that Dr. Susan Blackmore (a NDE experiencer herself) suggests that the loss of sensory input may help to induce these experiences. So with a malfunctioning temporoparietal junction and loss of much sensory input, it seems quite reasonable that the brain, in trying to model its version of reality, perceives itself in some hovering observer state. As for memories of operating room procedures or unusual dress (as has been reported in some rare cases), it may be possible that input from the senses may not be totally gone, but not consciously perceived, and reinterpreted from a newly constructed version of reality. The brain is incredibly complex and when one is trying to save a life, careful measurements of any low signals are understandably not being performed. In any case, it looks as though again, a materialistic explanation is likely sufficient.
What about the tunnel? During a NDE some report going through a tunnel after experiencing the OBE. Previously mentioned Dr. Susan Blackmore, at at one site shows a publication presented in The Skeptical Inquirer in which she discusses OBEs and then the tunnel. From the site:
In the 1930s, Heinrich Klüver, at the University of Chicago, noted four form constants in hallucinations: the tunnel, the spiral, the lattice or grating, and the cobweb. Their origin probably lies in the structure of the visual cortex, the part of the brain that processes visual information. Imagine that the outside world is mapped onto the back of the eye (on the retina), and then again in the cortex. The mathematics of this mapping (at least to a reasonable approximation) is well known.
Jack Cowan, a neurobiologist at the University of Chicago, has used this mapping to account for the tunnel (Cowan 1982). Brain activity is normally kept stable by some cells inhibiting others. Disinhibition (the reduction of this inhibitory activity) produces too much activity in the brain. This can occur near death (because of lack of oxygen) or with drugs like LSD, which interfere with inhibition. Cowan uses an analogy with fluid mechanics to argue that disinhibition will induce stripes of activity that move across the cortex. Using the mapping it can easily be shown that stripes in the cortex would appear like concentric rings or spirals in the visual world. In other words, if you have stripes in the cortex you will seem to see a tunnel-like pattern of spirals or rings.
This theory is important in showing how the structure of the brain could produce the same hallucination for everyone. However, I was dubious about the idea of these moving stripes, and also Cowan’s theory doesn’t readily explain the bright light at the center. So Tom Troscianko and I, at the University of Bristol, tried to develop a simpler theory (Blackmore and Troscianko 1989). The most obvious thing about the representation in the cortex is that there are lots of cells representing the center of the visual field but very few for the edges. This means that you can see small things very clearly in the center, but if they are out at the edges you cannot. We took just this simple fact as a starting point and used a computer to simulate what would happen when you have gradually increasing electrical noise in the visual cortex.
The computer program starts with thinly spread dots of light, mapped in the same way as the cortex, with more toward the middle and very few at the edges. Gradually the number of dots increases, mimicking the increasing noise. Now the center begins to look like a white blob and the outer edges gradually get more and more dots. And so it expands until eventually the whole screen is filled with light. The appearance is just like a dark speckly tunnel with a white light at the end, and the light grows bigger and bigger (or nearer and nearer) until it fills the whole screen. (See Figure 1.)
It looks like we get both the tunnel and the light described in terms of brain physiology.
The tunnel and light are also discussed here where the main point is made that the main features of NDEs are due to human physiology and neurochemistry that can arise in specific situations such as when the brain is deprived of oxygen. Since we all share a similar brain architecture and biochemistry, it really is no surprise that there are these shared objective experiences. Since we all accumulate different sets of experiences as we live, it also not surprising that the brain incorporates some of this into interpreting the new experiences into some type of model for reality and people will experience different things in an NDE as well.
With all this evidence that NDEs can be explained on a materialist basis, and with the overwhelming evidence that personality and consciousness (the very things you’d want to survive death) are firmly rooted in the physical structure of the brain, there is simply no need to hypothesize a life after death to explain anything. Earlier I said I wouldn’t mind an afterlife. It doesn’t matter what I want. I also wouldn’t mind several billion dollars in my bank account. Evidence seems to suggest I don’t have that much and so I’ll base my spending habits on that evidence.
Something that could support the case for an afterlife would need to be pretty remarkable. In many of the cases I’ve looked at, the person involved said they had a feeling of all questions being answered and filled with all knowledge. Unsurprisingly, this never seems to translate into anything specific that was not already known, or could not be pieced together from what was known. We’ve had nobody coming back to tell us whether string theory or quantum gravity (or neither) was correct and how to find out. Nobody has made specific predictions, such as a specific warning for 9/11. In one NDE I’ve read, the person reported back that the universe was teeming with life. He or she didn’t tell us where to point the radio telescopes. We weren’t told what form of life, if any, was under the ice at Europa (something we will eventually be able to verify).
So what is the lesson here? Without the consolation of life after death, what have we got? We get to no longer worry about how we’ll spend eternity. The actions we take here on earth should not be made on the presupposition of affecting one’s non existent afterlife, but to enhance life here on earth. To not only enrich your life with all the experiences you can, but to enrich your personal relationships. To help build up a better society for the future will suffering will be minimized and happiness and opportunity are available for all. This one life is the one chance you’ve got. It’s precious, so make it count.