Being a card carrying materialist, I've always felt that our mental life could be explained in physical terms. Although I consider myself a twinkie when it comes to appreciating deep philosophical debate, I really think Nagel's succinct summary of the main argument in his recent book "Mind and Cosmos" doesn't hold water, because it makes a basic category error that Metzinger has pointed out. More on that below, but first some clips of Nagel's summary, and a subsequent refutation by Kitcher.
The physical sciences can describe organisms like ourselves as parts of the objective spatio-temporal order – our structure and behavior in space and time – but they cannot describe the subjective experiences of such organisms or how the world appears to their different particular points of view. There can be a purely physical description of the neurophysiological processes that give rise to an experience, and also of the physical behavior that is typically associated with it, but such a description, however complete, will leave out the subjective essence of the experience – how it is from the point of view of its subject — without which it would not be a conscious experience at all.
So the physical sciences, in spite of their extraordinary success in their own domain, necessarily leave an important aspect of nature unexplained. Further, since the mental arises through the development of animal organisms, the nature of those organisms cannot be fully understood through the physical sciences alone. Finally, since the long process of biological evolution is responsible for the existence of conscious organisms, and since a purely physical process cannot explain their existence, it follows that biological evolution must be more than just a physical process, and the theory of evolution, if it is to explain the existence of conscious life, must become more than just a physical theory.Kitcher argues:
...Once he has set up the framework within which the possible positions will be placed, his arguments are not easy to resist. In my view, though, the framework itself is faulty.Contrary to the Newtonian vision in which everything would be explained on the basis of a small number of physical principles:
…since the 19th century — since Darwin, in fact — that has not been a convincing picture of how the sciences make their advances. Darwin did not supply a major set of new principles that could be used to derive general conclusions about life and its history: he crafted a framework within which his successors construct models of quite specific evolutionary phenomena. Model-building lies at the heart of large parts of the sciences, including parts of physics. There are no grand theories, but lots of bits and pieces, generating local insights about phenomena of special interest….The molecular biologist doesn’t account for life, but for a particular function of life (usually in a particular strain of a particular species). Nagel’s 19th-century predecessors wondered how life could be characterized in physico-chemical terms. That particular wonder hasn’t been directly addressed by the extraordinary biological accomplishments of past decades. Rather, it’s been shown that they were posing the wrong question: don’t ask what life is (in your deepest Newtonian voice); consider the various activities in which living organisms engage and try to give a piecemeal understanding of those.
First, philosophy and science don’t always answer the questions they pose — sometimes they get over them. Second, instead of asking what life and mind and value are, think about what living things and minds do, and what is going on in the human practices of valuing. This shift of perspective has already occurred in the case of life. A Nagel analog who worried about the fact that we lack a physico-chemical account of life, would probably be rudely dismissed; a kinder approach would be to talk about the ways in which various aspects of living things have been illuminated.
Nagel is in the grip of a philosophical perspective on science, once very popular, that the work of the last four decades has shown to be inadequate to cope with large parts of the most successful contemporary sciences. Because of that perspective, a crucial option disappears from his menu: the phenomena that concern him, mind and value, are not illusory, but it might nevertheless be an illusion that they constitute single topics for which unified explanations can be given. The probable future of science in these domains is one of decomposition and the provision of an enormous and heterogeneous family of models. Much later in the day, it may fall to some neuroscientist to explain the illusion of unity, a last twist on successful accounts of many subspecies of mental processes and functions. Or, perhaps, it will be clear by then that the supposed unity of mind and of value were outgrowths of a philosophical mistake, understandable in the context of a particular stage of scientific development, but an error nonetheless.I think the most coherent view of what is going on in our subjective mental experience is given by Thomas Metzinger in his book "The Ego Tunnel"….. I've extracted some points:
- What he calls the Ego Tunnel (or PSM) is a complex property of the global neural correlate of consciousness (NCC which are the subject of many books) - what make “Mineness” or “I” possible - a vastly reduced model of what is really 'out there.'
- It is a transparent mental image that allows the conscious experience of being a self to emerge. (Transparency is our not seeing the firing of neurons in our brain, only what they represent for us).
- The model at a given moment is transparent because the brain has no chance of discovering that is is a model - it is a higher order representation integrating its information in longer time window than the lower order information processing in smaller time windows.
- Our visual perception time window is much larger than the time windows of primary visual processing and so those more rapid underlying processes are completely invisible to it (the same thing as not being able to see the individual frames in a movie reel, because our visual integration time is much longer). It is a metabolically efficient, quick and dirty way of knowing only what our evolution has deemed it necessary for us to know.
-In this view, Consciousness is taken to be the space of attentional agency, that set of information currently active in our brains to which we can deliberately direct our high level attention. Low level attention is automatic and can be triggered by entirely unconscious events.
- Metzinger makes the further assertion that consciousness is epistemologically irreducible: one reality, one kind of fact, but two kinds of knowledge: first-person knowledge and third-person knowledge, that never can be conflated.
- There is a long list of ideas on why consciousness evolved, what it is good for, doing goal hierarchies and long-terms plans, enhancement of social coordination, etc....Old things in the evolution of consciousness are ultrafast and reliable (like qualities of sensory experience) and transparent. In contrast, abstract conscious thought is not transparent or fast, it is slow and unreliable, experienced as ‘made.’I like Metzinger's description of consciousness as a as a new kind of virtual organ - unlike the permanent hardware of the liver, kidney, or heart it is always present. Virtual organs form for a certain time when needed (like an immune response, or like desire, courage, anger)...they are a new computational strategy, that makes classes of facts globally available and allows attending, flexible reacting, within context. The fast acting hardware of our autonomic and neuroendocrine emotional chemistry evolved to support the new classes of transient virtual organs.