I think I shall have to write a number of posts on this exciting and idea-rich book by one of our best philosophers. Here is the first.
Short (128 pp.) and programmatic, Thomas Nagel's new book explores the prospects of an approach in the philosophy of mind that is naturalistic yet not materialistic. His approach is naturalistic in that he locates the source of the world's intelligibility in it, and not in a transcendent being such as God outside it. As Nagel rightly observes, "Theism pushes the quest for intelligibility outside the world." (p. 45)
Nagel's approach is also naturalistic in that he views mind as a biological phenomenon as it could not be if substance dualism were true. But while naturalistic, Nagel also rejects "psychophysical reductionism" or "reductive materialism." Thus he rejects naturalism as currently articulated without embracing any form of anti-naturalism such as theism. Nagel, we might say, seeks a middle path between theistic anti-naturalism and materialistic naturalism. The latter is just materialism which Nagel defines as follows:
Materialism is the view that only the physical world is irreducibly real, and that a place must be found in it for mind, if there is such a thing. This would continue the onward march of physical science, through molecular biology, to full closure by swallowing up the mind in the objective physical reality from which it was initially excluded. (37)
This is a useful definition. Materialism is either eliminativist or reductivist. Now obviously there is such a thing as mind, so eliminativism is not an option. (41) My arguments against it here. So the materialist must try to show that mind belongs to objective physical reality and that everything about it is understandable in the way everything else in objective physical reality is understandable. In this way materialism closes upon itself, explaining not only the world the mind engages, but the engaging mind itself. I agree with Nagel that reductive materialism is untenable.
Treading his via media between theism and materialism, Nagel reopens the case for neutral monism and panpsychism. How does he get to these positions? This is what I will try to figure out in this post.
Mind is a biological phenomenon. We are organisms in nature, not Cartesian egos contingently attached to physical bodies. But we are conscious organisms. We are subjects of such qualitative states as pleasure and pain, and we are individuals with a subjective point of view. If psychophysical reductionism fails, as both Nagel and I maintain, then physical science, even if it can explain our existence as organisms adapted to an environment, cannot explain our existence as conscious organisms. We are not just objects in the world, we are subjects for whom there is a world. Even if the first fact can be adequately explained by physical science, the second, our subjectivity, cannot be.
Given the failure of psychophysical reductionism, and given that mind is a biological phenomenon encountered only in conscious organisms that have evolved from pre-conscious organisms, evolutionary theory cannot be a purely physical theory. (44) The 'makings' of conscious organsims must already be present in pre-conscious life forms. In this way the mind-body problem spreads to the entire cosmos and its history. Thus "the mind-body problem is not just a local problem" that concerns such minded organisms as ourselves. (3)
Inanimate matter evolved into pre-conscious life forms, and these evolved into conscious life forms. Since conscious organisms qua conscious cannot be understood materalistically, the same is true of pre-conscious life forms: the reduction of biology to physics and chemistry will also fail. This is because life must contain within it the 'makings' of consciousness. That is my way of putting it, not Nagel's.
Turning it around the other way, if we are to have an adequate naturalistic explanation of conscious organisms, then this cannot be "a purely physical explanation." (44) And so Nagel floats the suggestion of a global (as opposed to local) neutral monism "according to which the constituents of the universe have properties that explain not only its [mental life's] physical but its mental character." (56) Conscious organisms are composed of the same ultimate stuff as everything else is. For this reason, neutral monism cannot be kept local but goes global or "universal." (57) The idea, I take it, is that even the merely physical is proto-mental, the merely living being even more so. When conscious organisms arrive on the scene, the proto-mental constituents achieve an arrangement and composition that amounts to mental life as we know it.
Now how do we get from this universal neutral monism to panpsychism? Well, a universal neutral monism just is panpsychism: the ultimate constituents of nature are all of them proto-mental. Mind is everywhere since everything is composed of the same proto-mental constituents. But it is equally true that matter is everywhere since there is nothing mental or proto-mental that is not also physical.
Thus we arrive at a position that is neither theistic nor reductively materialistic.
Let me now try to list the key premises/assumptions in Nagel's argument for his panpsychistic naturalism.
1. Consciousness is real. Eliminativist materialism is a complete non-starter.
2. Naturalism: Consciousness occurs only in conscious organisms, hence cannot occur without physical realization. Mind is a biological phenomenon. No God, no Cartesian minds. No substance dualism, no theism.
3. Reductive Materialism (psychophysical reductionism) is untenable.
4. Consciousness cannot be a brute fact. Mind is not an accident but "a basic aspect of nature." (16) It cannot be that consciousness just inexplicably occurred at a certain point in evolutionary history when organisms of a certain physical complexity appeared. The arrival of conscious organisms needs an explanation, and this explanation cannot be an explanation merely of their physical character. It must also explain their mental character. But this materialism cannot do. Hence "materialism is incomplete even as a theory of the physical world, since the physical world includes conscious organisms as its most striking occupants." (45)
5. Nature is intelligible. Its intelligibility is inherent in it and thus not imposed on it by us or by God. The intelligibility of nature is not a brute fact: nature doesn't just happen, inexplicably, to possess a rational order that is understandable by us. I take Nagel's position to be that intelligibility is a necessary feature of anything that could count as a cosmos. Thus it needs no explanation and surely cannot have a materialist one: it cannot possibly be the case that the intelligibility of nature arose at some time in the past via the operation of material causes. The universe is so constituted as to be understandable, and we, as parts of it, are so constituted as to be able to understand it. (16-17)
I accept all of these propositions except (2). So in a subsequent post I must examine whether Nagel's case against theism is stronger than his case for his panpsychism.