There are a number of reasons why I would hesitate to call myself a naturalist in philosophy. One is that I am unsure of the scope of the word ‘natural’. In modern physics, dark energy and dark matter are widely accepted as natural features of the universe, but physicists tell me that no-one really knows exactly what they are, or how they causally affect the visible universe. It was Einstein who used the word ‘spooky’ of quantum field theory, so I am not sure that we have any clear idea of what the nature of physical reality is any more, what sorts of causality it may contain, and what its limits may be. Thus if anyone says ‘I only believe in what is natural’, science has a long way to go before it can definitively say just what that excludes.
Related to this is the question of whether there is teleological causality or purpose in nature. Some naturalists think not, but there is no doubt that persons, at least, act for purposes, and there is no clear account of how such action can be correlated with, much less reduced to, forms of efficient causality. As Julian Huxley said, it does seem as though the universe has tended to move in the direction of increasing awareness of and control of nature, and this looks suspiciously like an increase of value or worth-whileness, which suggests some sort of teleology in nature, whether or not it helps to introduce a designer to account for it.
This in turn relates to the question of whether there exist objective moral values; that is, states or processes which are of intrinsic value, just for their own sakes, whether or not conscious beings think there are. Naturalists would generally tend to deny this, but such denial is not obvious. Philosophers like John McDowell and David Wiggins argue for an ‘enriched naturalism’ which can include moral values as part of the natural world, and that too seems to me an open question.
Objective aesthetic values may also have a place in the natural world, if some things or states really are more beautiful or elegant than others, whatever people might think. Many scientists work with an ideal of the mathematical beauty of the cosmos. Roger Penrose has confessed to being a sort of Platonist, thinking that the real basis of natural reality is a mathematical elegance, complexity, and integration, which transcends the merely spatio-temporal. Stephen Hawking has also toyed with the idea that our spacetime is a manifestation of a deeper elegant reality which he calls the ‘quantum vacuum’, which is not merely nothingness, but a supra-spatio-temporal reality ruled by elegant quantum laws. Whether this can still be called ‘naturalism’ is moot. It is certainly not the sort of substantive naturalism that insists that all truths must be stateable ultimately in terms of the natural sciences of our universe.
Matters become even more complicated when one tries, as Daniel Dennett does, to give a purely science-based account of consciousness. There is no question that neuroscience has provided invaluable information about the neural bases of consciousness in humans. But the occurrence of subjective feelings seems to provide an extra item of information about the occurrence of depression, for example, that is not always publicly accessible and that it resists any sort of precise and verifiable numerical scaling (as in ‘how depressed were you on a scale of 1 to 10?’). At best, brain scanning produces good evidence for how a person is feeling, but that evidence needs to be confirmed as accurate by the person whose feeling it is. It is hard to see how this situation can ever be improved.
There is also the matter of intensionality – the occurrence of neuronal activity in the brain, which it may be assumed is felt by the subject as, say, having a mental image of Big Ben, has the property of being ‘about’ Big Ben. Intensionality is this ‘aboutness’, which does not seem to be a physical property. Physical properties can state and perhaps measure events at a specific time and location. But there is no known physical value that can say what a mental image or neural event is ‘about’. To change the case, no amount of inspecting what goes on in Einstein's brain will reveal to us the theory of relativity.
This difficulty can be generalized as the problem of seeing how physical events, which presumably fall under general causal laws which have no purpose and see no value in how they operate, can be events of ‘understanding a theorem’ or ‘coming to see the reason for something’. Of course, we can speak of computers as thinking, even as understanding, but we know perfectly well that computers understand nothing. It may be open to a naturalist to say that one day computers will be able to do so, but that is a faith, not a scientific result.
And that is my basic problem. Naturalism seems to be a faith that the sort of problematic issues I have mentioned can all one day be resolved by improved scientific methods. Radically opposed to this faith is a more widely held view among the practising scientists I know that it is unlikely that the human brain will ever improve so far, and one ought perhaps to be more agnostic both about what science will accomplish, about the adequacy of present scientific knowledge, and about placing limits on the meaning of the word ‘natural’ which try to equate it with the word ‘physical’ or ‘material’. I should say that this is not to espouse any sort or dualism. That too, in the present state of things, would be a faith, and as it happens not a very popular one among philosophers. But do philosophers really have to be committed to a faith? Might it not be better to describe the complexity and diversity of our understandings of the world, and not force them into one Procrustean grand narrative, like ‘naturalism’?
