I woke up Saturday morning with a strange, unpleasant feeling in my stomach. I initially thought it was indigestion, but after a certain amount of reflection I diagnosed it as guilt. I feel my last post was a bit dismissive and defensive, and so I’d like to make recompense by giving a calmer and more considered response to Seth and Mitchell.
Response to Seth
I worry my post gave the impression that non-philosophers have no business engaging with philosophical questions (as Mitchell tweeted in response). In fact, I have very much valued Seth’s engagement with philosophy, for example, raising Chalmers’ distinction between the “hard” and “easy” problems and giving his own take on it. I shouldn’t be dismissing his engagement, as I did in my last post, just because he hasn’t read every last detail of Chalmers’ Two-Dimensional Argument against Materialism.
At the same time, I respectfully disagree his position, and I would like to articulate in a bit more detail the source of my disagreement. Seth claims that opposition to materialism is rooted in claims about what can be imagined. If this were all it amounted to, then as he says opponents of materialism would be open to the charge of mistaking a failure of imagination for an insight into necessity. But in my view, the opposition to materialism is rooted in the belief that the purely quantitative vocabulary of physical science is ill-suited to the task of capturing the qualities of conscious experience.
Here’s the basic premise on which I’d rest my case:
The Key Premise – A congenitally blind neuroscientist could never, through reading neuroscience in braille, come to know what it’s like to see colours.
It follows that language of neuroscience could never convey the qualities involved in colour experience; if a neuroscientific theory could convey the qualities involved in colour experience, it would be able to teach the blind what it’s like to see colours. And if neuroscience can’t even describe these qualities, then it certainly can’t reductively explain them. For a reductive explanation would involve describing these qualities and then accounting for their existence in terms of physical processes in the brain.
(For those who have looked into this debate in a lot of detail, of course it gets more complicated, requiring responses, for example, to the phenomenal concept strategy, but this is the starting point. The full argument can be found in the first half of my book).
My interest was piqued by Seth’s suggestion that predictive processing might provide resources to bridge this gap. I’d love to hear more details, but from what I know so far about predictive processing I can’t see how this could help. My test would be: Could a congenitally blind neuroscientist come to know what it’s like to see colours by reading about the predictive processing in the brain?
How can I prove that neuroscience alone will never bridge this gap? I can’t, but the conviction that it inevitably will seems to me an unjustified leap of faith. Perhaps the most common defence of this conviction, given by Seth and others, is to appeal to the track record of physical science. The fact that physical science has explained so much of our universe, it is claimed, ought to give us confidence that it will one day explain consciousness.
I have a different way of thinking about the history of science. The rightly celebrated success of the physical science began when Galileo declared that the qualities of consciousness were in the soul and so outside of its domain of natural science, which allowed physical science to focus exclusively on the purely quantitative properties of the physical world. In other words, physical science was designed as an inherently limited project, describing quantities and ignoring qualities. The fact that it has had great success in modelling quantities gives us no grounds for supposing it capable of dealing with qualities. But that’s precisely what a true theory of consciousness would need to do, as consciousness is an essentially quality-laden phenomenon. A reductive theory of consciousness would have to explain the colours, sounds, smells and tastes that characterize our inner subjective lives in terms of the physical properties of the brain.
Seth goes on to argue that people like me are expecting too much from a theory of consciousness:
“As long as we can formulate explanatorily rich relations between physical mechanisms and phenomenological properties, and as long as these relations generate empirically testable predictions which stand up in the lab (and in the wild), we are doing just fine. Riding behind many criticisms of current consciousness science are unstated intuitions that a mechanistic account of consciousness should be somehow intuitively satisfying, or even that it must allow some kind of instantiation of consciousness in an arbitrary machine. We don’t make these requirements in other areas of science…”
In fact, I do not expect anything more than correlations and predictions from neuroscience. But I would expect more from an empirical case for materialism. I think the materialist is obliged to provide reductive explanations of higher-level phenomena. For most other phenomena – life, water, heat – such reductive explanations are available, at least in principle. These explanations are intuitively satisfying. Why is it so hard to reductively explain consciousness? In the case of life, water and heat, what we are looking to explain are functional properties, that is to say, properties to do with how things behave, or how their parts behave. The quantitative language of physical science is well suited to this. But in the possibly unique case of consciousness we are dealing with qualities, and the quantitative language of physical science is simply not up to this task.
I can’t rule out materialism with 100% certainty, but many decades of hard work has, in my humble opinion, produced zero progress in the project of reductively explaining the qualities of consciousness. This is not surprising as the project of articulating the qualities of consciousness in quantitative language is on the face of it incoherent. Moreover, the drive to find a materialist solution to the problem of consciousness is unmotivated. In the 1920s Russell and Eddington did for consciousness science what Darwin did for the science of life (see below): They showed how to fit consciousness into our scientific story of the world. The job has already been done.
Having said all that though, I certainly wouldn’t want to stop materialists trying to explain consciousness in the language of physical science, and it would be a remarkable development if they ever managed to do it. One gets the impression reading Seth’s piece that he thinks anti-materialists are stopping neuroscientists making progress. But in so far as neuroscience is giving us correlations/explanations, it is neutral between materialism, dualism, and panpsychism. The proponents of these views would simply give different philosophical interpretations of the data: the materialist would see the physical states as constituting the conscious states, the dualist would see the physical states as causing the conscious states (in conjunction with basic psycho-physical laws of nature), the panpsychist would see the conscious states as the intrinsic nature of the physical states. In so far as some neuroscientists are trying to reductively explain consciousness, then of course they are pursuing a goal inconsistent with dualism/panpsychism. But a plurality of different theories are pursued in science and philosophy without it being a problem. Let a thousand flowers bloom!
Response to Mitchell
I think I learnt something from the exchange with Mitchell, and that is that my simplicity argument for panpsychism is dependent on my rejection of materialism (In fact, this is clear in my book, but has not been transparent in my non-academic work, such as the piece Mitchell discusses). If a standard kind of materialism is true, then consciousness is to be explained in terms of the (broadly construed) functional features of the brain. But that disqualifies consciousness from being an intrinsic property of the brain. The relevant distinction here is:
Functional properties – Properties that concern the behaviour of an entity, or the behaviour or its parts.
Intrinsic properties – Properties which are not purely functional properties, i.e. their nature cannot be entirely captured in terms of how its possessor is disposed to behave (or how its parts are disposed to behave).
(I appreciate this is a bit of a non-standard use of ‘intrinsic property’, but the usage has kind of stuck in these debates. Really I’m talking about what Derk Pereboom calls ‘absolutely intrinsic properties’, or what Chalmers calls ‘quiddities’.)
Premise 1 of my argument is that physical science tells us nothing of the intrinsic properties of matter: physical science merely tells us what stuff does not how it is. But if consciousness can be explained in terms of the functional properties of physical science, then premise 2 is false: consciousness is not an intrinsic property of the brain. On the other hand, if materialism is false and the properties of consciousness cannot be accounted for in terms of the functional properties of the brain, then conscious states do look like a good candidates for being the intrinsic properties of the brain. Therefore, the simplicity argument has force only if we already have good reason to think materialism is false.
This point is made clear by Mitchell’s analogy of my argument using the property of life. I take it that life is a functional property: for something to be alive is for it or its parts to exhibit various complex forms of behavioural functioning, e.g. growth, reproduction, etc. And for precisely this reason, the ‘panvitalist’ argument Mitchell outlines fails. If consciousness were also a functional property, then my argument for panpsychism would fail for the same reason.
But that’s okay, as I do think we have very strong reason to think materialism is false, as I explained in my above response to Seth. And that doesn’t mean my argument is circular. The argument is intended to show that panpsychism is the best view among the non-materialist options, e.g. dualism, neutral monism, etc. I’m grateful to Mitchell for helping to make this clear; it’s probably led to a lot of talking at cross purposes in the past.
Once the dependence on anti-materialism is made clear, I don’t think any of the other criticisms Mitchell makes have force (he’s welcome to correct me!). There is the common complaint that panpsychism doesn’t ‘explain’ or ‘predict’ anything. I agree that panpsychism can’t be directly tested, simply because consciousness itself cannot be directly observed. This is deep problem that raises worries for any theory of consciousness.
But I would disagree that panpsychism doesn’t explain anything. It accounts for consciousness, in the sense that it provides a place for consciousness in our scientific conception of the universe. We know that consciousness exists, and hence any theory of the world must be able to account for the reality of consciousness. I believe that materialism cannot account for the reality of consciousness and so must be false. Of the anti-materialist options that can account for the reality of consciousness, panpsychism is the simplest, which I think gives us strong reason to think it’s the one most likely to be true. If you like, you can think of it as an inference to the best explanation, as Hedda Hassel Morch suggested in the twitter exchanges. Of course panpsychism does not account for consciousness in more fundamental terms (although it may account for human consciousness in terms of more fundamental forms of consciousness), but the idea that we are obliged to do this seems to me a prejudice of materialism.