The metaphysical pitfall
Philosophical columns, part second

Much of modern philosophising can be understood as the twin activities of conceptual reduction and elimination, fueled by metaphysical considerations. Radical empiricists tell us that there are only 'sense impressions', or somesuch, and therefore every concept used in rational discours ought to be reducable to talk of sense impressions - if such a reduction does not seem feasible, the concept is to be eliminated. More relaxed empiricists accept that the empirical world contains much that we will never experience, and change their vision on reduction accordingly: every rationally permissible concept can be reduced to empirical concepts, and consequently every concept that cannot be so reduced ought to be abandoned. Naturalists - on at least one meaning of the term - may loosen their epistemological constraints even further, accepting facts about unobservable entities such as electrons; but the reductionist thesis remains important: everything ought to be reducable to concepts found in the study of nature. Morality, self-consciousness, intentionality, teleology, potentiality, necessity, freedom - all of these must either be reduced to the unproblematic realm of natural knowledge, or else exposed as the sham they are, and abandoned altogether. Let us call the general idea behind all these strategies, namely that all rational discourse can in principle be reduced to the concepts of natural science, 'natural reductionism'.

Almost every natural reductionist will exclude mathematics and logic from the reductionist requirement. These fields of knowledge are often seen as quite independent of the natural world, often as a priori, certainly as not empirical. However, it is not easy to see why mathematics and logic can escape the requirements of natural reductionism, while moral discours, or the intentionality of thoughts, cannot. Some say it is a matter of certainty; but is it more certain that there are infinitely many prime numbers than that it is morally wrong to kill babies? Both seem beyond doubt; and indeed, it is easier to imagine that we have missed some subtle mistake in our proofs that the number of primes is infinite than that it will turn out to be good to kill babies. Perhaps the difference is that mathematics is a priori, and the others a posteriori; or that mathematics is analytical and the others synthetic. But the fact that our thoughts have the feature of 'aboutness' - something which is not easily reducible to physical concepts - does not seem any less a priori than the truths of mathematics. And who can say whether 'human agents have free will', 'killing babies is evil' or 'I am self-conscious' are analytic or synthetic - if that question is even meaningful? It is not even uncontroversial that mathematics is analytic. What makes the realms of logic and mathematics distinct from that ofnatural science, but does not in the same stroke free the realms of morality, intentionality and possibility from the demands of natural reductionism? If this cannot be explained, the reductionist program is problematic. But we will not now pursue this line of thought further: there are deeper worries.

A century of analytic philosophy has made clear just how much the reductionist thesis will cost us. If we start with nothing but the plain, unadorned facts that tell us which events took place in the natural world, as described by physics, and the apparatus of standard logic, we will not be able to salvage very much. There is no satisfactory reduction of the concept of 'causality' to this sparse basis, nor of that of 'law of nature'. 'Possibility' and 'necessity' cannot be reduced either, and the entire world of counterfactuals goes down with them. When we reduce the mental to the physical, the strongly related concepts of 'choice' and 'free will' are either eliminated or twisted beyond recognition. The physical structures that will have to portray our thoughts and feelings cannot exhibit the kind of 'aboutness' we were wont to talk about before the project of reduction was undertaken. Perhaps most distressingly, we appear to lose any significant notion of 'the good' - reducing it to mere pragmatics or social determination will not give us the kind of guide towards a meaningful life that we have come to expect. If we undertake the project of natural reductionism in a serious way, we will be creatures no longer truly human, living in a world that has lost most of its meaning.

That does not prove that the thesis underlying natural reductionism is false: claiming that the world is nothing more than the collection of physical facts and has no further structure and no further meaning is coherent and consistent, even if it actually adopting this outlook leads to unattaractive consequences. But it makes us pause and reconsider the foundations of natural reductionism: if the price is so high, there had better be very compelling reasons for us to adopt this position. What are these reasons? Mainly this: our best theories about the world state that there is nothing more than the particles, fields, interactions and such that physics describes. Therefore, there cannot be anything in the world that is not reducible to these things; and hence, when we talk about the world, we must in the last analysis be talking about these kinds of entities; or else, about logical relations between concepts. Natural reductionism is the consequence of a thoroughly physicalist outlook. By 'physicalism' I will mean the point of view that nothing exists but the actual physical events of our world.

So, why accept physicalism? Why would the only tools available in the rational study of morality, for instance, be those of physicists or other natural scientists? The only way I can see to make physicalism, and with it natural reductionism, inescapable is to argue along the following lines. The conclusions reached through rational discourse are non-arbitrary. For if they were arbitrary you could simply claim anything, and that would not be rational - rational knowledge is objective, not subjective. The only way to make conclusions about the world non-arbitrary is by paying attention to experience, and experience alone. Now the only experience we have of the world is experience of physical facts. Therefore, all rational knowledge about the world (and that includes ourselves) must be reducible to knowledge about physical facts. Therefore, physicalism is true, or at least a good basis for epistemology. This argument has no doubt impressed many; but I take it to be utterly false.

I take the argument for physicalism to be false, because I do not believe that all experience we have can be captured in the terms of physics - we do not simply experience physical facts. Look at a table. You experience a table, and an integral part of this epxerience is the fact that you can put things on this table, that you can sit or stand on this table, that you can duck beneath it, move it around, and interact with it in numerous other ways. You may not do any of these things, and perhaps you never will - they are hardly physical facts. But all the possibilities are part of your experience of the world: you live in a world of possibilities and impossibilities, of purpose and story. Look at your computer screen: perhaps you'll see buttons. You know what they do, what happens when you click your mouse on them; and you know all the other ways in which you can interact with the screen, and you know what everything on the screen means, and what its purpose is. Now imagine someone from a pre-technological culture experiencing the same screen - would it be the same experience? Most certainly not! Yet the physical situation is the same. So the world of experience has structure beyond the merely physical: the structure of possibility, of interaction, of all kinds of narrative - but there is more, there are elements of experience which the language of physics cannot capture. You experience the intentionality (the 'aboutness') of your thoughts. You experience moral outrage and respect. You experience the many roads of self-discovery. You experience free will and the possibility of choice. You even experience as clearly as you experience anything the movement of time - something which physical theories are notoriously unable to capture. The empricial world goes far beyond the physical, and hence the argument for physicalism given above does not hold water. (Continental philosophers have been saying this for ages, but how many of us have listened?)

It is of course possible that all these experiences are illusions and do not reflect the true structure of reality. But what reason have we to believe this? To simply postulate physicalism at this point does not help - the plausibility of physicalism depends on disregarding all the above experiences, and cannot function as an independent reason for disregarding them. No, I put forward the claim that there is no good reason to disregard all these large parts of our experience that are absolutely fundamental to living a meaningful human life. The fact that we can build a pretty and coherent picture of the impoverished world that remains when we cut them out is certainly no such reason.

And this is the metaphysical pitfall: if we restrict ourselves to one part of our experience, we are often able to build a coherent world view out of it, which in turn can be used to argue that the part of experience we took into account is privileged and the only real one. If we start with nothing but physics, we will never get morality - and this failure can be used to argue that there is no moral reality. Hence, the restriction to physics is legitimate. This is of course a very vicious circle, but because our metaphysical viewpoints may shape our thought to a very large extent, it is all to easy to loose sight of this fact. Instead, we start believing that the world which we have willfully impoverished is the real one, and all our inverstigations will seem to confirm this. This is a trap of which we must ever beware.

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