Sharp Blue: Argument against an afterlife

The close correlation of conscious experience with neural activity in the brain makes the existence of an afterlife extremely unlikely. An obvious example of this correlation is the way in which drugs or injuries can modify the functioning of parts of the brain and induce changes in consciousness. An anaesthetic can “switch off” consciousness, hallucinogenics can cause conscious experience of things that don’t really exist except in the data sets shuffled by the brain, and injuries to specific regions of the brain can produce strikingly weird changes in the sufferer’s ability to think about the world. Even in brains that are functioning normally, we can use methods like functional PET scans to deduce which regions of the brain are involved in which types of thought. In some cases, we can even map the way in which streams of information are processed at successively higher levels by suborgans of the brain. We can also get insight into the way in which thoughts are generated by study of cognitive illusions, experiments on different types of memory and the transformation of data between them.

Despite our inclination to think otherwise, human minds are not general-purpose, undifferentiated thinking machines but incredibly complex software using all sorts of specific data representations and functions acting on those representations. (Again, I’ve slipped into using computational language. I don’t mean to imply that brains are computers, but the neurons certainly carry information around within the brain and modify it in various ways. It’s just easier to talk about data and functions.) Given all this, I think it’s fair to say that conscious experience correlates very closely with these neural events.

Now, destruction of specific regions of the brain (through injury or catastrophic internal events like strokes) can totally destroy a person’s ability to think in certain ways or, even more strikingly, to experience the results of those thoughts. An example here is the phenomenon of “blindsight”, in which people have no conscious experience of sight but can still have the information obtained from vision in their model of the world. A person with blindsight might still be able to catch a thrown ball, even without “seeing” that ball. There are thousands of other examples. Furthermore, they are cumulative: subsequent destruction of other regions of the brain will blot out other parts of the mind or other aspects of consciousness. I think that it’s not unreasonable to consider that the destruction of the entire brain will blot out the whole of the subject’s consciousness. This being the case, the existence of an afterlife seems to me to be highly unlikely.

Suppose there is still an afterlife. This means that some of these transformations must only affect the mind and not the “soul”. But for it to be a meaningful afterlife, some of the deceased’s identity must persist. This in turn means that some parts of the physical activity of the brain must affect the soul. Certainly, memory must persist, and that’s encoded in physical structures in the brain. Furthermore changes in personality should persist. My experiences have shaped my ways of thinking about the world, and I’d like to carry my current mode of thinking into any afterlife. Again, these modes of thought are embodied in physical structures in the brain. It seems inevitable that some physical changes in the brain must lead to changes in the soul that persist into any possible afterlife. However, there are many, many changes in the brain going on all the time. For there to be an afterlife, there would have to be something that decides which of these changes are beneficial and which deleterious. These are not easy decisions to make, and they need to me made at the level of specific changes to single neurons. This would require godlike[1] degrees of computation. Maybe even more computation than can be done using the entire resources of the universe. Perhaps there isn’t even a clean separation into good and bad changes so the whole thing is impossible.

Even given all of this, I still don’t see the point. If there’s an afterlife, then why not just skip straight to that rather than having a life first? (Furthermore, I doubt that evolution could result in an afterlife composed of entities that have no further effect on the material world. An afterlife would require there to be some other agency involved in the unfolding of the history of life and then why bother with evolution?)

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[1] Someone subsequently pointed out that God is supposed to be quite godlike.