“It has become clear that our bodies and central nervous systems are parts of the physical world, composed of the same elements as everything else and completely describable in terms of the modern versions of the primary qualities— more sophisticated but still mathematically and spatiotemporally defined. Molecular biology keeps increasing our knowledge of our own physical composition, operation, and development. Finally, so far as we can tell, our mental lives, including our subjective experiences, and those of other creatures are strongly connected with and probably strictly dependent on physical events in our brains and on the physical interaction of our bodies with the rest of the physical world.” – Thomas Nagel, Mind and Cosmos, Chapter 3.
With these words, Nagel begins to tell us about how the tremendous recent developments in biology and neuroscience have raised hopes for a materialist explanation of life and consciousness. Science has made great strides in demonstrating the detailed workings of biology and brain function. Yet, with all the scientific progress, the connection between mind and physical biology seems as elusive as ever. Some philosophers have even taken the position that Nagel calls “eliminative materialism” in which mental events are illusory.
Nagel looks historically at conceptual approaches to solving the problem because he thinks that reductionism alone will not discover an answer. A conceptual approach is based on adding something new to science in the hopes of providing the necessary leverage for new discovery. This is similar to the approach of David Chalmers who has called for adding back into the scientific picture a fundamental quality of subjective experience.
Chalmers approach is to include within the science of consciousness the science of subjective experience, including the psychological and sociological implications of our mental states. It is difficult to tell whether Nagel would agree with Chalmers. Nagel thinks that whatever is added to science would need to be at least as radical as electromagnetic fields and relativity theory. Here Nagel has written something very surprising from the viewpoint of science history. The most radical scientific developments in the twentieth century were quantum physics and relativity theory, not electromagnetic fields and relativity theory. Electromagnetic fields were definitively added to science in the 19th century by James Clerk Maxwell. I wonder if he has chosen to write “electromagnetic fields” in order to preserve some hope for quantum explanations of consciousness.
Nevertheless, Nagel’s description of the difficulty of avoiding dualism has challenged me. As I have pursued the path of quantum explanations for consciousness, I have concentrated on the power of quantum calculation to bring about order. There is real order producing power in quantum computation that lends itself to a possible explanation for mental activity if consciousness is seen as a type problem solving.
However, there is nothing in the computational model of quantum physics that can produce subjective experience. I have worked over thirty years in computer systems design and programming and there is no way that classical computation alone will produce consciousness or subjective experience. There must be a qualitative difference between classical computation and quantum computation that allows for the addition of a subjective sense of intent or purpose to quantum computation. The type of subjective sense added to quantum calculation would probably need to be optional because it could not be required to be present for such non-conscious quantum calculations as take place in ordinary physics (for example, in lasers). And if it is optional, or “contingent” as Nagel would say, then it must be considered a dualistic explanation.
The non-dualist solution to this problem takes me to George Berkeley, whom Nagel mentions in passing and whose idea of “subjective idealism,” Nagel completely discounts. Berkeley was an 18th century philosopher whose perspective developed as a counterpoint to the new discoveries in science and the trend away from theism. Berkeley’s Idealism is the point of view that everything is mind and that all matter originates in God’s mind, and he maintains that view without denying the objective existence of material objects. Some of his ideas influenced Albert Einstein and his view of the role of consciousness in the act of perception has new echoes in quantum physics. But few thinkers these days give much credence to idealism. I think that Berkeley’s idealism takes on fresh meaning when seen through the lens of quantum physics.
Another non-dualist approach would be to discount subjective experience. Those favoring a behaviorist approach would be happy with this line of reasoning. If quantum computation is at the core of our mental ability, then that could explain our mental problem solving ability but it would leave unexplained any subjective experience. Those who view subjective experience as an unnecessary byproduct of evolution, like the color of blood, might find this view attractive. But it has the unfortunate consequence of turning us into zombies.
At this point in chapter 3, Nagel has left us with a significant puzzle: (1) there is no non-dualist materialist theory of consciousness that can explain subjective experience; (2) Idealist and theistic theories are not welcome; and (3) dualism leaves too much room for theistic explanation and therefore it is also not welcome. I await his recommendation for something new to be added to the description of the physical world, because at this point, I am feeling challenged but also slightly unwelcome.