Nagel on Consciousness

In the later chapters of his book called Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature is Almost Certainly False, Thomas Nagel claims that the current materialist model cannot explain the human mind, consciousness, rationality or moral assessment.

Consciousness is the most conspicuous obstacle to a comprehensive naturalism that relies on the resources of physical science. The existence of consciousness seems to imply that the physical description of the universe, in spite of its richness and explanatory power, is only part of the truth, and that the natural order is far less austere than it would be if physics and chemistry accounted for everything. If we take this problem seriously, and follow out its implications, it threatens to unravel the entire naturalistic world picture (p.35).

Mechanisms of belief that have a selective advantage in the everyday struggle for existence do not warrant our confidence in the construction of theoretical accounts of the world as a whole. I think the evolutionary hypothesis would imply that although our cognitive capabilities could be reliable, we do not have the kind of reason to rely on them that we ordinarily take ourselves to have in using them directly—as we do in science. In particular, it does not explain why we are justified in relying on it to correct other cognitive dispositions that lead us astray, though they may be equally natural, and equally susceptible to evolutionary explanation. The evolutionary story leaves the authority of reason in a much weaker position. This is even more clearly true of our moral and other normative capacities—on which we rely to correct our instincts (p.28).

Our own existence presents us with the fact that somehow the world generates conscious beings capable of recognising reasons for action and belief, distinguishing some necessary truths and evaluating the evidence for alternative hypotheses about the natural order. We don’t know how why this happens, but it is hard not to believe there is some explanation of a systemic kind—an expanded account of the order of the world.

We go on using perception and reason to construct scientific theories of the natural world even though we do not have a convincing external account of why those faculties exist that is consist with or confidence in their reliability (p.31).

An account of their biological evolution must explain the appearance of conscious organisms as such.

Since a purely materialist explanation cannot do this, the materialist version of evolution theory cannot be the whole truth. Organisms such as ourselves do not just happen to be conscious. Therefore, no explanation even of the physical character of those organisms can be adequate which is not also an exploration of their mental character. In other words, materialism is incomplete even as a theory of the physical world, since the physical world includes conscious organisms among its most striking occupants.

So long as the mental is irreducible to the physical, the appearance of conscious physical organisms is left unexplained by a naturalist account of the familiar type. On a purely materialist understanding of biology, consciousness would have to be regarded as a tremendous and inexplicable extra brute fact about the world.

Selection for physical reproductive fitness may have resulted in the appearance of organisms that are in fact conscious, and that have the observable variety of different specific kinds of consciousness, but there is no physical explanation of why this is so, nor any other explanation that we know of. (p. 45).