NATURALISM, MATERIALISM AND FIRST PHILOSOPHY D.M. ARMSTRONG In the first section of this paper I define and defend a spatio-temporal account of the general nature of reality. I call this doctrine "Naturalism". In the second section I define and defend the somewhat more specific, although still very general, doctrine of Materialism or Physicalism. (I take it to be a sub-species of Naturalism.) However, if we define ontology or "first philosophy" as the most abstract or general theory of reality, then it seems that neither Materialism nor even Naturalism is an ontology. In the third section I sketch very briefly the ontology which I favour. Unlike that adopted by many Naturalists and Materialists, it ad- mits both particulars and universals. It is Realistic, not Nominal- istic. I maintain, in particular, that only by adopting a Realistic (but not Platonistic) account of universals can the Naturalist and the Materialist solve the pressing problems of the nature of causa- tion and of law-like connection. I Naturalism Naturalism I define as the doctrine that reality consists of nothing but a single all-embracing spatio-temporal system. It is convenient here to distinguish this proposition from the weaker claim that reality at least contains as a part a spatio-temporal system. I will say something in defence of the weaker claim first, and then defend the view that reality is nothing but this spatio- temporal system. It is difficult to deny that a spati-temporal system appears to exist. But, of course, many philosophers have denied that this appearance is a reality. Leibniz is an example. He held that reality consists of the monads and that space and time are illusions, even 261 D.M.ARMSTRONG if illusions which have some systematic link with reality. Leibniz was at least a pluralist. But for Parmenides, for Hegel and for Bradley, reality is not a plurality but is simply one. "[he spatio- temporal system is an appearance which completely or almost completely misrepresents the one. I will not spend any time considering such views, despite their importance. The arguments used to establish them are all a priori. I believe that they can all be answered. But in any case, as an Empiricist, I reject the whole conception of establishing such results by a priori argumentation. But the Naturalist may seem to face a challenge to the view that there is a spatio-temporal system from a source which he must take more seriously: from natural science itself. It is the impression of an outsider like myself that some speculations in fundamental physics lead to the conclusion that, at deep levels of explanation, space and time dissolve and require to be replaced by other, more fundamental, principles. However, I suggest that such speculations need not perturb the Naturalist. I believe that he should draw the familiar dis- tinction between denying that a certain entity exists and giving an account of that entity in terms of other entities. It is a very extreme view to deny that the world has spatio-temporal features. I find it hard to believe that even the most far-fetched specu- lations in fundamental physics require such a denial. But it in- volves no such denial to assert that the spatio-temporal features of things can be ultimately analyzed in terms which do not involve any appeal to spatio-temporal notions. The Naturalist, as I have defined Naturalism, is committed to the assertion that there is a spatio-temporal system. But M~y is he committed to asserting that spatio-temporality cannot be analyzed in terms of non-spatio- temporal principles? What is not ultimate may yet be real. I suppose that if the principles involved were completely different from the current principles of physics, in particular if they involve appeal to mental entities, such as purposes, we might then count the analysis as a falsification of Naturalism. But the Naturalist need make no more concession than tiffs. Consider, as a parallel example, the attitude of Materialists towards purposes. There are some Materialists who deny that men and other organisms have purposes. This seems to me to be a quite foolish position to adopt. Materialism may be true - my hypo- thesis is that it is true - but it is a speculative doctrine. The existence of purposes, on the other hand, is a plain matter of fact. The prudent Materialist will therefore argue in the following way. 262 NATURALISM, MATERIALISM AND FIRST PHILOSOPHY There is no reason to believe that what it is for an organism to have a purpose involves anything more than the operation of purely physical processes in the organism. (These mechanisms are, pethaps, very sophisticated cybernetic processes.) In this way, an account of purposes is proposed in terms of processes which do not themselves involve purpose. No doubt this is a somewhat deflationary view of what a purpose is. But it is a view of the nature of purposes, not a denial of them. Spatio-temporality may be analyzed, just as the Materialist claims that purpose can be analyzed. However, in default of some quite extraordinary analysis of spatio-temporality - say, in terms of spiritual principles - Naturalism is not thereby falsified. But, just as it is an incredible view that purposes can be analyzed away, so, I think, it is an incredible view that spatio-temporality could be analyzed away. A priori reasoning should not convince us of the unreality of space and time. Nor, I have just argued, is it at all plausible that a posteriori reasoning will ever drive us to the same conclusion. So much by way of brief defence of the positive content of Naturalism. I turn now to its negative contention: that the world is nothing more than a spatio-temporal system. Here we find that philosophers and others have postulated a bewildering variety of additional entities. Most doctrines of God place him beyond space and time. Then there are transcendent universals, the realm of numbers, transcendent standards of value, timeless propositions, non-existent objects such as the golden mountain, possibilities over and above actualities ("possible worlds"), and "abstract" classes, including that most dilute of all entities: the null-class. Dualist theories of mind are interesting intermediate cases, because they place the mind in time but not in space. The same holds for some theories of God and also, apparently, for Karl Pepper's recently proposed "third world" of theories which interacts with the "sec- ond" world of mind (Popper 1973). Despite the incredible diversity of these postulations, it seems that the Naturalist can advance a single, very powerful, line of argument which is a difficulty for them all. The argument takes the form of a dilemma. Are these entities, or are they not, capable of action upon the spatio-temporal system? Do these entities, or do they not, act in nature? In the case of many of these entities, they were at least originally conceived of as acting in nature. God acted in the world. The Forms in Plato's Phaedo are causes, and the Forms were apparently transcendent universals, as well as being transcendent 263 D.M. ARMSTRONG numbers and transcendent standards of value. Descartes' spiritual substances interact with matter, and Pepper's "third world" inter- acts with the "second world" of mind, which in turn interacts with material things. Nevertheless, there are very great difficulties involved in hold- ing that any of these transcendent entities act upon the spatio- temporal system. First, there are logical or conceptual difficulties. A great many of these entities are not thought of as capable of change. This holds for transcendent universals, the realm of numbers and values, propositions, non-existent objects, possible worlds and abstract classes. In many theological systems, God is taken not to change. Now in typical cases of causation, one change brings about an- other. It follows that, if these entities work causally in the world, they do not work in this typical way. How, then, do they work? Could they be conceived of as sustaining certain features of the natural world, or as exerting some sort of steady, unchanging pressure upon it which, when certain circumstances arise in nature, gives rise to certain effects? Such a notion is perhaps barely possible, but the actual identification of such alleged causal opera- tion is a major difficulty. For instance, where sustaining causes are postulated in nature, hypotheses about such causes can be tested by observing situations where the alleged sustaining cause is ab- sent. If the alleged effect is also absent, the hypothesis is sup- ported. But no such verification is possible, even in principle, in the case of unchanging entities. In the Parmenides 133b-134e, Plato goes so far as to raise logical difficulties for the conception of any relation at all (and so afortiori, a causal one) between the Forms and spatio-temporal particulars. Even in the relatively straightforward case of the interaction of spiritual substance with material body, conceptual difficulties have been raised. For instance, the impossibility of specifying any mechanism or other explanation of how the spirit acts upon its body has been thought to be a problem. Descartes himself, as evidenced in particular by his correspondence with Princess Eliza- beth, thought that the action of spirit on matter involved some conceptual difficulty. In the case of many of the postulated transcendent entities, there never was any thought of crediting them with causal power in the natural world. Possible worlds, for instance, are not thought to act upon the actual world. But even in the case of entities originally credited with power in the natural world, considerations 264 NATURALISM, MATERIALISM AND FIRST PHILOSOPHY of the sort just sketched have been an important pressure towards denying that they had such power.