Reduction and Elimination in Philosophy and the Sciences
Reduction and Elimination in Philosophy and the Sciences
Reduction and Elimination in Philosophy and the Sciences
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
A Metaphysically Moderate Version of Humean Supervenience<br />
Szilárd Koczka, Miskolc, Hungary<br />
Humean Supervenience (HS) is <strong>the</strong> doctr<strong>in</strong>e that <strong>the</strong> nomic<br />
features of our world supervenes on <strong>the</strong> arrangement of<br />
basic, non-nomic properties. David Lewis's motivation <strong>in</strong><br />
elaborat<strong>in</strong>g HS was to present a view which does not refer<br />
to properties <strong>and</strong> relations alien to physics, so it is<br />
extremely important for <strong>the</strong> defender of HS to make it<br />
compatible with current physics. Contrary to Lewis,<br />
philosophers known as necessitarians or governists claim<br />
that laws express necessary relations. These claims<br />
<strong>in</strong>volve an implicit ontological commitment that Lewis<br />
summarizes as follows „...<strong>the</strong>re are more th<strong>in</strong>gs <strong>in</strong> heaven<br />
<strong>and</strong> earth than physics has dreamt of.” (Lewis 1994,474).<br />
With<strong>in</strong> a non-humean ontological framework <strong>the</strong>re<br />
can be states of affairs which are metaphysically related. A<br />
non-humean approach can be plausible only if <strong>the</strong><br />
defenders of this view can put forward a conv<strong>in</strong>c<strong>in</strong>g<br />
argument to <strong>the</strong> po<strong>in</strong>t that <strong>the</strong> very notion of a natural law<br />
<strong>in</strong>volves a non-humean ontology. Whe<strong>the</strong>r one can acquire<br />
such an argument is dubious, <strong>and</strong> as humean analyses do<br />
not require such extra entities to expla<strong>in</strong> <strong>the</strong> role of laws <strong>in</strong><br />
science, it seems that <strong>the</strong> ontologically less comitted<br />
humean view is <strong>the</strong> promis<strong>in</strong>g one. For <strong>the</strong> rest of <strong>the</strong><br />
paper I will assume that <strong>the</strong>re is no such argument around.<br />
It is clear, that philosophical accounts of scientific<br />
laws appeal to metaphysical <strong>in</strong>tuitions, but <strong>the</strong>re is a<br />
significant difference between <strong>in</strong>vok<strong>in</strong>g <strong>in</strong>tuitions or<br />
metaphysical <strong>the</strong>ories. If one tries to analyse <strong>the</strong> notion of<br />
scientific laws <strong>in</strong> terms of his favorite metaphysical <strong>the</strong>ory,<br />
<strong>the</strong> proposed analysis assumes that <strong>the</strong> background<br />
metaphysical <strong>the</strong>ory is already accepted. As Lange (2000)<br />
emphasises: without a previously established metaphysical<br />
framework, this k<strong>in</strong>d of approach is unillum<strong>in</strong>at<strong>in</strong>g. But if<br />
we keep <strong>in</strong> m<strong>in</strong>d that a philosophical account of <strong>the</strong> natural<br />
laws is to be fitted with scientific practice, <strong>the</strong>n it seems <strong>the</strong><br />
weaker metaphysical commitment <strong>the</strong> philosophical<br />
account has <strong>the</strong> better. Scientists do not employ fully<br />
developed metaphysical <strong>the</strong>ories, but <strong>the</strong>y surely know<br />
how to work with <strong>the</strong>se laws.<br />
Formulations of Humean Supervenience<br />
Lewis's orig<strong>in</strong>al formulation of HS can be summarized as<br />
follows: In <strong>the</strong> actual world, everyth<strong>in</strong>g supervenes on local<br />
qualities <strong>in</strong>stantiat<strong>in</strong>g at certa<strong>in</strong> po<strong>in</strong>ts of space-time. There<br />
is no difference between two possible worlds without some<br />
difference <strong>in</strong> <strong>the</strong>se local qualities. As Loewer (1996) po<strong>in</strong>ts<br />
out, Lewis's motivation was to defend physicalism aga<strong>in</strong>st<br />
philosophical challenges. Thus HS is motivated by a tendency<br />
to avoid appeal to non-physical entities. However,<br />
Lewis's (1986) own formulation postulates local properties<br />
which seems to contradict current <strong>the</strong>ories <strong>in</strong> quantum<br />
mechanics. It seems that if our current quantum mechanics<br />
is correct, <strong>the</strong>n we have to ab<strong>and</strong>on <strong>the</strong> view that <strong>the</strong>re<br />
are local properties at all. Lewis <strong>in</strong> his (1986,xi) admitted<br />
that his formulation – as a physicalist doctr<strong>in</strong>e – can be<br />
falsified by empirical research, if it excludes <strong>the</strong> possibility<br />
of his local properties; <strong>in</strong> this sense HS is at best a cont<strong>in</strong>gent<br />
truth.<br />
Loewer argues that for an acceptable doctr<strong>in</strong>e we<br />
need to ref<strong>in</strong>e <strong>the</strong> Humean Supervenience <strong>the</strong>sis <strong>in</strong> order<br />
to make it compatible with recent physics. Loewer(1996)<br />
claims that <strong>the</strong> problem of def<strong>in</strong><strong>in</strong>g <strong>the</strong> Humean Base (HB)<br />
on which everyth<strong>in</strong>g else supervenes can be solved by<br />
appeal<strong>in</strong>g to <strong>the</strong> ma<strong>the</strong>matical apparatus of quantum<br />
physics. Accord<strong>in</strong>g to his solution, <strong>the</strong> HB can be<br />
characterized as consist<strong>in</strong>g of po<strong>in</strong>ts of <strong>the</strong> fundamental<br />
ma<strong>the</strong>matical space which is used by current quantum<br />
mechanics. Earman <strong>and</strong> Roberts (2005) have some<br />
misgiv<strong>in</strong>gs about Loewer's version of HS. They argue that<br />
different physical <strong>the</strong>ories use different ma<strong>the</strong>matical<br />
spaces, <strong>and</strong> <strong>the</strong>re is no uncontroversial way to determ<strong>in</strong>e<br />
which ma<strong>the</strong>matical treatment is <strong>the</strong> fundamental one. If<br />
we try to specify <strong>the</strong> HB as <strong>the</strong> fundamental magnitudes of<br />
<strong>the</strong> best future physical <strong>the</strong>ory HS – without an account of<br />
what makes a <strong>the</strong>ory 'physical' – will be vacuous. It is<br />
possible that future physics postulates several k<strong>in</strong>ds of<br />
entities which are alien to our current <strong>the</strong>ories.<br />
There are two possible answer to <strong>the</strong> question of<br />
HS's compatibility with recent physical <strong>the</strong>ories: (i)To make<br />
HS compatible with recent physics a neo-humean<br />
philosopher have to def<strong>in</strong>e <strong>the</strong> HB on which everyth<strong>in</strong>g<br />
else supervenes. As Earman <strong>and</strong> Roberts emphasize: at<br />
this po<strong>in</strong>t our orig<strong>in</strong>al metaphysical problem turns to be an<br />
epistemological one. (ii)There is a possible alternative to<br />
<strong>the</strong> epistemological account that Schaffer (2008) has <strong>in</strong> his<br />
m<strong>in</strong>d while he defends reductionism as a <strong>the</strong>sis about<br />
m<strong>in</strong>d-<strong>and</strong>-<strong>the</strong>ory <strong>in</strong>dependent reality. He writes: “Causation<br />
<strong>and</strong> <strong>the</strong> laws of nature are noth<strong>in</strong>g over <strong>and</strong> above <strong>the</strong><br />
pattern of events, just like a movie is noth<strong>in</strong>g over <strong>and</strong><br />
above <strong>the</strong> sequence of frames.” (Schaffer 2008).<br />
Accord<strong>in</strong>g to his view, we do not need to def<strong>in</strong>e precisely<br />
what k<strong>in</strong>d of properties belong to <strong>the</strong> HB s<strong>in</strong>ce this<br />
formulation of HS does not concern <strong>the</strong> subvenient base. It<br />
is important that Schaffer does not even refer to basic<br />
(microphysical) facts. His start<strong>in</strong>g po<strong>in</strong>t is <strong>the</strong> manifest<br />
image, so it does not matter that whe<strong>the</strong>r we can def<strong>in</strong>e<br />
basic microphysical facts with <strong>the</strong> help of our best <strong>the</strong>ories.<br />
However this approach relies on <strong>the</strong> presupposition that<br />
knowledge about m<strong>in</strong>d <strong>in</strong>dependent reality can be acquired<br />
via metaphysical <strong>in</strong>quiry of <strong>the</strong> manifest image. Beh<strong>in</strong>d<br />
<strong>the</strong>se presuppositions is <strong>the</strong> view that we have knowledge<br />
about <strong>the</strong> natural laws. This is what I doubt. For a<br />
m<strong>in</strong>imalist viewpo<strong>in</strong>t if it is possible to come out with a<br />
metaphysically less committed approach of nomic notions,<br />
it seems that <strong>the</strong>re are no much reason to hold such a<br />
view. Thus if <strong>the</strong>re is a formulation of (i) which can h<strong>and</strong>le<br />
our philosophical problems about scientific laws, we can<br />
disapprove (ii). My solution relies on a dist<strong>in</strong>ction between<br />
natural laws (of which we does not have knowledge) <strong>and</strong><br />
scientific laws. I th<strong>in</strong>k that <strong>the</strong> debate can be mean<strong>in</strong>gful<br />
only if we start with <strong>the</strong> notion of a scientific law <strong>and</strong> <strong>the</strong>n<br />
try to answer <strong>the</strong> question as to what philosophically<br />
relevant implications it may have.<br />
Natural laws or scientific laws?<br />
Metaphysical discussions of natural laws assume that<br />
science aims to discover <strong>the</strong> laws of nature. Consequently,<br />
a metaphysical account of <strong>the</strong> natural laws can be accepted<br />
only if it can expla<strong>in</strong> <strong>the</strong> role of <strong>the</strong> laws <strong>in</strong> scientific<br />
practice. Non-humeans argue that <strong>the</strong> notion of scientific<br />
law required by science can only be expla<strong>in</strong>ed with<strong>in</strong> a<br />
non-humean metaphysical framework. Humeans (e.g.<br />
Loewer 1996) argue that HS does expla<strong>in</strong> <strong>the</strong> role of <strong>the</strong><br />
notion of scientific laws <strong>and</strong> we do not need non-Humean<br />
181