Monday, 23 July 2012

The Principle of Naturalistic Closure and Naughty Metaphysics

A couple of people asked me what I meant by "polemics", in the previous post. I was referring to a recent book, Ladyman & Ross et al. 2007, Every Thing Must Go: Metaphysics Naturalized, whose Preface begins:
This is a polemical book. One of its main contentions is that contemporary analytic metaphysics, a professional activity engaged in by some extremely intelligent and morally serious people, fails to qualify as part of the enlightened pursuit of objective truth, and should be discontinued.
As a kind of criterion for identifying the allegedly naughty metaphysics which "should be discontinued", Ladyman & Ross et al. introduce to The Principle of Naturalistic Closure, denoted PNC:
The Principle of Naturalistic Closure
Any new metaphysical claim that is to be taken seriously at time t should be motivated by, and only by, the service it would perform, if true, in showing how two or more specific scientific hypotheses, at least one of which is drawn from fundamental physics, jointly explain more than the sum of what is explained by the two hypotheses taken separately, where this is interpreted by reference to the following terminological stipulations:

Stipulation: A ‘scientific hypothesis’ is understood as an hypothesis that is taken seriously by institutionally bona fide science at t.

Stipulation: A ‘specific scientific hypothesis’ is one that has been directly investigated and confirmed by institutionally bona fide scientific activity prior to t or is one that might be investigated at or after t, in the absence of constraints resulting from engineering, physiological, or economic restrictions or their combination, as the primary object of attempted verification, falsification, or quantitative refinement, where this activity is part of an objective research project fundable by a bona fide scientific research funding body.

Stipulation: An ‘objective research project’ has the primary purpose of establishing objective facts about nature that would, if accepted on the basis of the project, be expected to continue to be accepted by inquirers aiming to maximize their stock of true beliefs, notwithstanding shifts in the inquirers’ practical, commercial, or ideological preferences. (Ladyman & Ross (et al) 2007, Every Thing Must Go, pp. 37-8.)
It seems to me that there are problems with PNC, at least as stated, and the crucial phrase is
"metaphysical claim"
A definition of this is repudiated. But, for example, are claims like,
i) spacetime contains closed timelike curves
ii) spacetime permits hypercomputation
to be counted as metaphysical? The question is not whether they are scientific or not (they are scientific, in some reasonable sense). The question is whether they are metaphysical or not.

One might think, with some logical empiricists, that no scientific claim is a metaphysical claim. But then that just rules out naturalized metaphysics.

If, on the other hand (as seems reasonable to me), there is non-trivial overlap between metaphysical claims and scientific claims, then it would be useful to obtain some guidance as to how to identify the claims in the overlap, even if the guidance is a bit vague.

There presumably are also metaphysical claims which are somehow non-scientific (perhaps the existence of possible worlds, or transfinite cardinals, the existence of angels dancing on pins, etc.), but this raises demarcation questions about what a scientific claim is. If one adopts a sufficiently holistic epistemology, then - at least in principle, through pragmatic, coherence and simplicity considerations, but still conditioned by sensory experience - such questions become amenable to rational acceptance/rejection. (Quine's view.)


  1. Jeffrey, it seems to me that you are on ecumenical mission to incorporate a great many claims into contemporary metaphysics. Correct me if I am wrong, but it would seem that anything that does or might make a difference as to the state of the universe is thereby, by your lights, eo ipso metaphysics. On the other hand, it seems to me, a lot of proponents of contemporary metaphysics are engaged in questions that cannot possibly make such a difference. I admit to a scientistic bias here, of course, but when we start taking seriously the question of whether half of Ringo is part of the Beatles — that's when I get off the bus.

  2. I assume that you are selecting some of the most polemical stuff here and that there might be some substance to the rest of the book, but I must say, that that Principle of Naturalistic Closure seems so ridiculous as to beggar belief. The requirement of being taken seriously by "institutionally bona fide science" borders on the, well I don't know what, I have so far deleted 'insane', 'delusional' and 'fascistic'.

    I have no problem with ontic structural realism (which I believe the book is mostley about), except that I fundamentally disagree with it, but the setting up of a toy methodological model that just happens to make most of metaphysics except ontic structural realism and related "naturalised" metaphysics defunct is, well, words again fail.

    I am often left wondering how it is that at a time when the one thing we know FOR SURE about current fundamental physics is that it is definitely wrong (until a QT incorporates or obviates GR) the anglophone philosophical world has made a fetish object of theoretical physics.

    Just to Aldo, Dirac felt that beyond its experimental failure, the deeper problem with classical physics was it's failure to give a satisfactory ontological account of the "particle", and that this was one of the triumphs of QT. Mucking about with parts and wholes to try and see if a language as formal as the langage of 'some' and 'all' and 'every' embodied in predicate logic is surely not a totally trivial exercise. Also the top half of Ringo was definitely a part of the Beatles

  3. Hi Aldo, thanks.
    Your suggestion - does it make a difference? - might be thought of as related to a conservativeness criterion for metaphysics, analogous to Hilbert's program (infinitary set theory). It's reminiscent of the pragmatism of Peirce and James too (Jody Azzouni as well, who has argued that the disappearance of mathematicalia would make no difference). In some older papers about deflationary truth theories, Stewart Shapiro and I separately suggested that truth theories count as "deflationary" when conservative (we noted that compositional truth is non-conservative: e.g., PA + compositional truth (with induction extended) yields consistency of PA).
    I think there is a significant overlap: some claims of logic, mathematics and physics are also metaphysical to some extent, but I don't have a good criterion. Given there is an overlap, I can't quite see why some research that is at the same time logical, mathematical & metaphysical (or incorporates ideas from theoretical physics) should be discontinued.

    More specifically, it looks to me like certain work on spacetime violates PNC. E.g., spacetimes with CTCs (Gödel); the theory of hypercomputation in Malament-Hogarth spacetimes; supertasks more generally. But it seems that PNC implies that this should be discontinued.

    Ringo's nose was a very important part of The Beatles!!

  4. Joseph, thanks - "the setting up of a toy methodological model that just happens to make most of metaphysics except ontic structural realism and related "naturalised" metaphysics defunct is, well, words again fail."

    Yes, that's the trouble, a kind of purification demand. Perhaps not quite fascistic! I don't think there are any physicists who would be able to spot the alleged huge methodological difference between
    i. a paper on ontic structuralism discussing haecceities,
    ii. a paper on the mereology of spacetime gunk, or supertasks, or the recent fibre-bundle geometric substantialism of Arntzenius & Dorr (i.e., the extension of Field's program to gauge theories).

    It would help if ontic structuralism was a position that had been given a precise formulation. One finds views like it in Russell's Introduction to Mathematical Philosophy (1919), Analysis of Matter (1927), Carnap's Aufbau, Quine's "Ontological Reduction and the World of Numbers", and "Ontological Relativity". I think the key here is to understand the problem of Leibniz equivalence. But this is a very difficult topic ...

    The only precise formulation I know so far is one that uses Ramsey sentences to make "structural representation claims"; but that version has trivialization problems, for reasons explained by Newman in his famous 1928 discussion of Russell's structuralism.

    The alternative, defended in Ladyman & Ross et al. 2007 is to talk of "real patterns", following Dennett, but I am not convinced there is a mathematically satisfactory account of these.