MIND AND COSMOS: WHY THE MATERIALIST NEO-DARWINIAN CONCEPTION OF NATURE IS ALMOST CERTAINLY FALSE by Thomas Nagel
But to explain consciousness, as well as biological complexity, as a consequence of the natural order adds a whole new dimension of difficulty, I am setting aside outright dualism, which would abandon the hope for an integrated explanation. Indeed, substance dualism would imply that biology has no responsibility at all for the existence of minds. What interests me is the alternative hypothesis that biological evolution is responsible for the existence of conscious mental phenomena, but that since those phenomena are not physically explainable, the usual view of evolution must be revised. It is not just a physical process. If that is so, how much would have to be added to the physical story to produce a genuine explanation of consciousness--one that made the appearance of consciousness, as such, intelligible, as opposed to merely explaining the appearance of certain physical organisms that, as a matter of fact, are conscious? It is not enough simply to add to the physical account of evolution the further observation that different types of animal organisms, depending on their physical constitution, have different forms of conscious life. That would present the consciousness of animals as a mysterious side effect of the physical history of evolution, which explains only the physical and functional character of organisms. . . For a satisfactory explanation of consciousness as such, a general psychophysical theory of consciousness would have to be woven into the evolutionary story, one which makes intelligible both (1) why specific organisms have the conscious life they have, and (2) why conscious organisms arose in the history of life on earth. . . [S]ome kind of psychophysical theory must apply not only nonhistorically, at the end of the process, but also to the evolutionary process itself. That process would have to be not only the physical history of the appearance and development of physical organisms but also a mental history of the appearance and development of conscious beings. And somehow it would have to be one process, making both aspects of the result intelligible. . . This would mean abandoning the standard assumption that evolution is driven by exclusively physical causes. Indeed, it suggests that the explanation may have to be something more than physical all the way down. The rejection of psychophysical reductionism leaves us with the mystery of the most basic kind about the natural order--a mystery whose avoidance is one of the primary motives of reductionism. It is a double mystery: first, about the relation between the physical and the mental in each individual instance, and second, about how the evolutionary explanation of the development of physical organisms can be transformed into a psychophysical explanation of how consciousness developed. The existence of consciousness is both one of the most familiar and one of the most astonishing things about the world. No conception of the natural order that does not reveal it as something to be expected can aspire even to the outline of completeness. And if physical science, whatever it may have to say about the origin of life, leaves us necessarily in the dark about consciousness, that shows that it cannot provide the basic form of intelligibility for this world. There must be a very different way in which things as they are make sense, and that includes the way the physical world is, since the problem cannot be quarantined in the mind. . . This dissatisfaction with an explanatory stopping place that relates complex structures to complex structures is what underlies the constant push toward reduction in modern science. It is hard to give up the assumption that whatever is true of the complex must be explained by what is true of the elements. That does not mean that new phenomena cannot emerge at higher levels, but the hope is that they can be analyzed through the character and interactions of their more elementary components. Such harmless emergence is standardly illustrated by the example of liquidity, which depends on the interactions of the molecules that compose the liquid. But the emergence of the mental at certain levels of biological complexity is not like this. According to the emergent position now being considered, consciousness is something completely new. Because such emergence, even if systematic, remains fundamentally inexplicable, the ideal of intelligibility demands that we take seriously the alternative of a reductive answer to the constitutive question--an answer that accounts for the relation between mind and brain in terms of something more basic about the natural order. If such an account were possible, it would explain the appearance of mental life at complex levels of biological organization by means of a general monism according to which the constituents of the universe have properties that explain not only its physical but its mental character.
