The Metaphysics Within Physics
Maudlin (Tim)
Source: Maudlin (Tim) - The Metaphysics Within Physics
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Introduction (Full Text)

  1. The essays that compose this book were written over a span of more than a decade, and were not originally conceived of as part of a larger philosophical project. But it transpires that they collaborate: all have been fashioned from the same clay and molded by the same concerns. The basic idea is simple: metaphysics, insofar as it is concerned with the natural world, can do no better than to reflect on physics. Physical theories provide us with the best handle we have on what there is, and the philosopher's proper task is the interpretation and elucidation of those theories. In particular, when choosing the fundamental posits of one's ontology, one must look to scientific practice rather than to philosophical prejudice.
  2. From this point of view, a distressing amount of philosophical energy appears to be invested in questionable projects. For example, it has been a long-standing philosophical problem to provide an ‘analysis' or an ‘account' or a 'reduction' of laws of nature in terms of something else, such as relations between universals1 or patterns of local quantities. But nothing in scientific practice suggests that there should be such an analysis (unlike, say, genes which are explicable in terms of underlying physio-chemical structure). The first essay argues simply this: laws of nature stand in no need of ‘philosophical analysis'; they ought to be posited as ontological bedrock.
  3. The most frequent objection to this ‘primitivist' view of laws is that it stands in opposition to an influential metaphysical picture that David Lewis advocates and elaborates in many of his works. The metaphysical picture goes by the name of Humean Supervenience2:
      Humean supervenience3 is named in honor of the greater [sic] denier of necessary connections. It is the doctrine that all there is to the world is a vast mosaic of local matters of fact, just one little thing and then another. (But it is no part of the thesis that these local matters of fact are mental.) We have geometry: a system of external relations of spatio-temporal distance between points. Maybe points of spacetime itself, maybe point-sized bits of matter or aether fields, maybe both. And at those points we have local qualities: perfectly natural intrinsic properties which need nothing bigger than a point at which to be instantiated. For short: we have an arrangement of qualities. And that is all. All else supervenes4 on that.
      ...(Lewis 1986a5, p. x)
  4. Accepting Humean Supervenience6 severely constrains one's ontological resources and correspondingly poses a daunting set of metaphysical challenges. Given only a patterned set of local qualities arrayed through space-time, one must derive laws, causes, truth conditions for counterfactuals, a direction of time, dispositions, objective chances, and so on. Lewis set his hand to these projects, and many more have followed. There is work enough here to sustain a large cadre of philosophers for many generations.
  5. The Humean project is very seductive: one is given a delimited set of resources and set the task of expressing truth conditions for some class of propositions in those terms. To win the game is to get the truth conditions to come out in a way that is, largely, intuitively correct. Proposed solutions can be counter-exampled, counter-examples can be reinterpreted, intuitions can be bartered off against each other. If a proposed analysis fails, there is always the hope that one more widget, one extra subordinate clause, can set things right again. No end of cleverness can be deployed both on offense and defense.
  6. For all that, I think that the Humean project, as Lewis conceived it, is unjustifiable. Why think that all there is to the world is ‘a vast mosaic of local matters of fact'? Why accept these strong constraints on one's ontology in the first place? I take up these questions in the second Chapter: ‘Why Be Humean?'
    And it is not just that the Humean picture is too impoverished, that it postulates less than there is. The metaphysical atoms it utilizes are instances of repeatable (or qualitatively identical) local properties. These are also elements of the basic ontology of non-Humeans such as David Armstrong. But modern gauge theories paint a different picture: they provide an account of the physical nature of the world that does not employ such properties. This novel approach to the problem of universals7 is the subject of Chapter 3, ‘Suggestions from Physics for Deep Metaphysics'.
  7. As the project of reducing natural laws provides employment for metaphysicians, so the game of analyzing the nature of the ‘arrow of time' occupies philosophers of science. The problematics are very similar: on the one hand, laws are claimed to be nothing but patterns in the physical state of the world; on the other, the direction of time is supposed to be nothing but a matter of how physical contents are disposed across the space-time manifold. And corresponding to primitivism about laws is a primitivist approach to the arrow of time: it is a fundamental, irreducible fact that time is directed. Chapter 4, ‘On the Passing of Time', defends this view.
  8. So among the first four essays we have the following conclusions: the Humean project is unjustified, in that both laws of nature and the direction of time require no analysis, and is misconceived, in that the atoms it employs do not correspond to present physical ontology. But I do not wish to become a primitivist about everything. In particular, physical theory does not employ a notion of causation8 at a fundamental level, so causal locutions are proper candidates for reduction. Some efforts in this direction, consonant with my preferred ontology, are made in Chapter 5, ‘Causation9, Counterfactuals, and the Third Factor'.
  9. Scattered among these five papers, then, lies the outlines of an ontology based in physics. Only once the papers were written, however, did their joint import become clear to me. In particular, taking both the laws of nature (as laws of temporal evolution) and the direction of time as primitive allows one to produce a sort of causal explanation of the fundamental Humean entity: the Humean Mosaic, or the total physical state of the universe. These disparate threads are pulled together in Chapter 6, ‘The Whole Ball of Wax'. A final brief reflection on method in metaphysics can be found in the Epilogue.
  10. If there is one major topic related to these papers that deserves more extensive treatment, it is Ockham's Razor. The Razor, like Humean Supervenience10, generates much employment for philosophers: the more parsimonious the ontology, it is said, the better. Why believe in irreducible laws of nature if some passable replacement can be found simply in the patterns in the mosaic? Why believe in an intrinsic direction to time if the gradient of entropy always points the same way? Entia non sunt multiplicanda praeter necessitatem, and the availability of a reduction obviates any necessity. Surely we should be seeking the slenderest basis on which to erect our ontology.
    But it is not clear that the Razor can withstand much critical scrutiny. If by necessitas one means logical necessity, then the Razor will land us in solipsism. But if one means something milder — entities ought not to be multiplied without good reason — then the principle becomes a harmless bromide: nor should one's ontology be reduced without good reason. The Razor cannot be derived from a simple logical observation — that the subjective probability one assigns to the existence of one set of items must always decrease when one enlarges the set—since the Razor recommends positive disbelief in the additional ontology. Such disbelief engenders errors if the controversial items exist: if the universe has been profligate, then the Razor will lead us astray.
  11. Why, then, has the Razor been so widely accepted? No doubt, in many cases it yields the correct conclusion: explanations that require elaborate conspiracies and coincidences are less often true than simpler alternatives. But this result can frequently be derived straight from confirmation theory: simpler theories are commonly better confirmed by the data than competitors with equants and epicycles11. Yet this does not mean that the theory with the smaller ontology is always better confirmed. And questions about how one confirms — or disconfirms — claims about the ontological status of natural laws or the direction of time are bound to be extremely contentious.
  12. So rather than a general theory of justification for ontological commitment, I have produced only some case studies. These studies suggest that the Razor, and the accompanying mania for ontological reduction, is overrated. The concepts of the laws of nature and of the passage of time play central roles in our picture of the world, and the arguments that these can, or need to be, reduced to something else strike me as flimsy. If the ontology that arises most naturally from reflection on physics is too rich for Ockham or Hume or Lewis, then so much the worse for them. Let others subsist on the thin gruel of minimalist metaphysics: I'll take my ontology mit Schlag.
  13. A final note on the structure of these papers. Each was written to stand alone, rather than as part of a larger work. So each can be read independently of the others, but there is a corresponding need for some repetition and redundancy among them. On the theory that it is easier to skip what is familiar than to retrieve what is not, I have left them as they are. To any hardy soul who soldiers through them all: my thanks and my apologies.

In-Page Footnotes

Footnote 5: See "Lewis (David) - Philosophical Papers Volume II".

Footnote 11: Clark Glymour's bootstrapping confirmation theory, for example, has as a consequence that certain sorts of 'deoccamized' theories will be less well confirmed than the theories from which they are generated (Glymour 1980, pp. 143ff.).

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