I’m a naturalist, an out-and-out naturalist, a philosophical or metaphysical naturalist, a naturalist about concrete reality. I don’t think anything supernatural or otherwise non-natural exists.
You can’t classify anything as supernatural or non-natural until you have a substantive conception of the natural in relation to which something can be classified as non-natural. I do have one: I take it that concrete reality – anything that exists in space-time – is entirely physical. I’m a physicalist naturalist, and I think metaphysical naturalism is the same thing as physicalism as I’ve just defined it (I’m putting ethics aside). There are, however, important questions to be raised about what this amounts to. They’re old questions, but they haven’t received enough attention recently. One result of this is that many – probably most – philosophers who call themselves naturalists are in fact extreme anti-naturalists. They’re false naturalists – noturalists.
Something very strange has happened to the use of the word ‘naturalism’ in the last fifty years or so, when it comes to the question of conscious experience (‘experience’ for short). W.V. Quine, who in his reductive passion and ontological austerity was seen as a standard bearer for naturalism in philosophy, never for a moment doubted or denied the existence of experience, as some of the false naturalists appear to do (even as they deny that they do). Quine never denied the existence of what he called ‘experience in all its richness … the heady luxuriance of experience’. No serious naturalist could deny it. Nevertheless, beginning in the 20th century, self-styled naturalists have seemed to think that questioning or doubting or denying the existence of experience is part of a thoroughgoing naturalism.
How did this happen? It began with the transmogrification of behaviourism early in the 20th century. Behaviourism started out in a highly fruitful way, as a moderate methodological thesis in psychology: roughly, that it’s not worth studying the phenomena of experience, although they obviously exist, because they’re not susceptible of scientifically rigorous quantitative treatment. It turned into a mad metaphysical thesis in philosophy, according to which there is nothing more to experience than behaviour and dispositions to behaviour: i.e., bluntly put, experience doesn’t really exist. Things got worse, especially after the publication of J.J.C. Smart’s paper ‘Sensations and Brain Processes’ in 1959. The denial of the existence of experience came to be thought of as naturalistic independently of any behaviourist (or ‘functionalist’) assumptions. The dubious existence or non-existence of experience was thought to follow simply from the fact – the view – that everything is wholly physical.
Here there is a wonderful irony, for the false naturalists – even as they doubt or deflate or deny the existence of experience, and revile Descartes, their favourite target, for being an outright realist about experience – are themselves in the grip of a fundamentally Cartesian conviction: the conviction that experience can’t possibly be physical, that matter can’t possibly be conscious. The irony is fierce because Descartes was at bottom aware that one can’t rule out the possibility that matter may be conscious. Many of the false naturalists, by contrast, have no such doubts.
Some of them will deny this. They will insist that they do admit the existence of consciousness or experience, and do allow that it can be physical. But they do this by changing the meaning of the word ‘conscious’ into something that involves no consciousness. They ‘looking-glass’ the term, by which I mean use it in such a way that whatever they mean by it, it excludes what the term actually means.
If physicalism is true, experience (consciousness) is wholly physical. For it certainly exists, and everything is wholly physical if physicalism is true. It follows that there are things about the nature of the physical that physics doesn’t characterise, because it doesn’t characterise the nature of experience. Some say that the word ‘physical’ is to be defined by reference to physics, so that if physics doesn’t characterise the nature of something, then it isn’t physical. But this is wrong. The word ‘physical’ is what is known as a ‘natural-kind’ term (like ‘iron’ or ‘water’), albeit of a highly general sort, and it’s generally allowed that we can be very wrong about the nature of anything denoted by a natural-kind term. So we may be very wrong about the physical. We can’t be sure we know the nature and limits of the physical. So we can’t be sure we know the nature and limits of the natural: we can’t be sure we know the nature and limits of the natural even if we’re right (I’m assuming we are) that the natural is the physical.
This is putting it mildly, because physics and cosmology are in turmoil. It’s not just that we don’t definitely know the nature and limits of the physical. We definitely don’t know the nature or limits of the physical. It doesn’t help much to say that we have a clear fix on the physical inasmuch as we know that the physical is the spatio-temporal, because we’re very far from clear about the nature of space-time. We may be very wrong about it, even after Einstein. A considerable number of physicists and cosmologists think that the description of reality as spatio-temporal is superficial.
It’s sometimes said that, for all our uncertainty, we have a pretty good fix on the basic nature of the physical. David Lewis once claimed that ‘the physical nature of ordinary matter under mild conditions is very well understood.’ But this isn’t true. It isn’t true even when we put aside the point that the known phenomena of experience are wholly a matter of the physical nature of ordinary matter under mild conditions (the mild if special conditions that obtain in the brain), along with the point that the physics and neurophysiology of the brain don’t enable us to understand how this is so. Even putting these things aside, we’re left with profound theoretical uncertainty about the nature of the ‘fundamental particles’, for example, and this uncertainty obviously extends to all conditions in which the fundamental particles are found, including all mild conditions. The same goes for gravity, ‘dark energy’, ‘dark matter’.
A physicalist conception of the natural has, nevertheless, a great deal of substance. I take it that vast numbers of the claims of current physics are either straightforwardly true or very good approximations to truth. The periodic table is on to something fundamental about the ultimate nature of concrete reality. So are formulae like F=ma, E=mc2, the inverse square law of gravitational attraction, and so on.