Posts Tagged ‘physics’


24 January 2008

I view reality in terms of scientific reductionism. I believe in the natural, but not the supernatural. In fact, I would consider everything that exists to be natural by definition, so that the word “supernatural” is a contradiction in terms. I believe that science presents the best method of knowing nature that human beings have yet discovered.

For this reason, there is something I find especially mysterious about the phenomenon of consciousness. Human beings are nothing but complex assemblies of atoms. We are literally nothing but protons, neutrons, and electrons assembled in a fantastically complex pattern. Somehow this dance of particles and energy that I call me has a feeling of existence, an inner reality of subjective experience. How can that be?

Note that when I speak of being mystified by consciousness, I am not referring to intelligence, knowledge, or any externally measurable property of a human being. As a thought experiment, I can easily imagine a physical universe like ours, with physical laws, with a planet like this one, on which life evolves. That life could attain a level of neurological complexity that allows it to be intelligent and inventive. Such life could develop language and technology. The members of this intelligent species could even exhibit emotional-looking reactions to various stimuli. But would it be necessary that they internally experience this ineffable soul-like experience I call consciousness?

Let me approach this from a different angle. If consciousness is an emergent property of physical matter arranged a certain way, then it should be possible in principle for human beings to create machines that experience consciousness. It may be that such machines could be constructed using existing computer technology such as silicon transistors. Alternatively, there may be some property possessed by animal nerve cells that is lacking in silicon transistors for building a conscious machine. But regardless of the details of the technology, it should in principle be possible for us to create a machine that is sufficiently similar to a human brain that it can likewise experience first-person subjective experience. After all, our brains contain nothing other than protons, neutrons, and electrons.

In this thought experiment, my question becomes, if you did build a conscious machine, how would you know you succeeded? Regardless of the observable behavior of the machine, a skeptic could argue that the behavior is an impressive simulation of a conscious being’s behavior, but does not prove consciousness is the source of the behavior. In fact, this is the age-old philosophical problem of solipsism, in which one can never be sure whether other people exist, let alone whether they are conscious in the same way we are. I am comfortable ignoring such musings, raising to the level of postulate that my sensory impressions of other people are trustworthy to attest to their existence, and further that sharing similar brain structure with others of my species implies sharing the trait of subjective mental experience with them also.

Here we find the crux of the problem of consciousness as confronted by scientific thinking. Science deals with objective observations that can be made by independent observers. For example, the relationship between the length of a pendulum’s string and the amount of time it takes to swing back and forth is something that people all around the world can try for themselves and all agree on the results. Consciousness, on the other hand, is not observable, except by being the entity that is conscious. In solipsist terms, I’m certain that I am conscious, but I’m not sure about you being conscious. I’m pretty sure you are, but I can’t prove it, because I can’t directly experience anyone’s consciousness but my own.

Beyond the limits of treating consciousness scientifically, there is an even more basic indescribable feeling of amazement I have when I quietly reflect on this topic. It comes attached to a certain thought, which is: how can this happen? How can my inner life feel so real, as if it were a universe to its own, and yet be caused exclusively by the action of physical laws? It indicates that somewhere in my thinking is a contradiction, but I have no idea where to look.