Reduction and Elimination in Philosophy and the Sciences
Reduction and Elimination in Philosophy and the Sciences
Reduction and Elimination in Philosophy and the Sciences
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Rule-Follow<strong>in</strong>g <strong>and</strong> <strong>the</strong> Irreducibility of Intentional States<br />
Antti Heik<strong>in</strong>heimo, Jyväskylä, F<strong>in</strong>l<strong>and</strong><br />
1. <strong>Reduction</strong> through Functional Def<strong>in</strong>ition<br />
It is not always clear what exactly is meant when it is said<br />
that someth<strong>in</strong>g mental is reducible to someth<strong>in</strong>g physical.<br />
Thus, when debat<strong>in</strong>g about reductionism, it is important to<br />
keep <strong>in</strong> m<strong>in</strong>d just which k<strong>in</strong>d of reduction one is talk<strong>in</strong>g<br />
about. One clearly def<strong>in</strong>ed <strong>and</strong> plausible notion of reduction<br />
comes from Jaegwon Kim. Reducibility is often taken<br />
to be a relation between two “levels”, such as <strong>the</strong> mental<br />
<strong>and</strong> <strong>the</strong> physical level. Kim argues, plausibly <strong>in</strong> my op<strong>in</strong>ion,<br />
that so called bridge-laws that connect <strong>the</strong> two levels with<br />
empirical regularities, do not amount to reduction (Kim<br />
2005, 103-5). This is because both <strong>the</strong> higher- <strong>and</strong> <strong>the</strong><br />
lower-level phenomena need to be mentioned <strong>in</strong> a statement<br />
of a regular connection between phenomena at two<br />
different levels, whereas reduction requires an account of<br />
<strong>the</strong> higher-level phenomenon solely <strong>in</strong> terms of <strong>the</strong> lower<br />
level. I take this much to be common ground between most<br />
reductionists <strong>and</strong> non-reductionists – that it is not enough<br />
for <strong>the</strong> reductionist to establish empirical connections between<br />
<strong>the</strong> mental <strong>and</strong> <strong>the</strong> physical. He/She needs someth<strong>in</strong>g<br />
stronger. In Kim’s view this stronger requirement is:<br />
138<br />
Conceptual connections, e.g., def<strong>in</strong>itions, provid<strong>in</strong>g<br />
conceptual/semantic relations between <strong>the</strong> phenomena<br />
at <strong>the</strong> two levels. (Kim 2005, 108)<br />
These conceptual connections serve as <strong>the</strong> first step of a<br />
reductive explanation, <strong>in</strong> terms of <strong>the</strong> “base” level, of <strong>the</strong><br />
phenomenon to be reduced. The reductive explanation<br />
consists of three steps:<br />
Step 1 (functionalization of <strong>the</strong> target property)<br />
Property M to be reduced is given a functional def<strong>in</strong>ition<br />
of <strong>the</strong> follow<strong>in</strong>g form: Hav<strong>in</strong>g M =def. hav<strong>in</strong>g<br />
some property or o<strong>the</strong>r P (<strong>in</strong> <strong>the</strong> reduction base doma<strong>in</strong>)<br />
such that P performs causal task C.<br />
Step 2 (Identification of <strong>the</strong> realizers of M) F<strong>in</strong>d <strong>the</strong><br />
properties (or mechanisms) <strong>in</strong> <strong>the</strong> reduction base<br />
that perform <strong>the</strong> causal task C.<br />
Step 3 (Develop<strong>in</strong>g an explanatory <strong>the</strong>ory) Construct<br />
a <strong>the</strong>ory that expla<strong>in</strong>s how <strong>the</strong> realizers of M<br />
perform task C. (Kim 2005, 101-2)<br />
On this model, <strong>the</strong>n, <strong>the</strong> reduction of a higher-level property,<br />
such as be<strong>in</strong>g a gene, consists of (1) a functional<br />
def<strong>in</strong>ition, such as “be<strong>in</strong>g a gene = def. be<strong>in</strong>g a mechanism<br />
that encodes <strong>and</strong> transmits genetic <strong>in</strong>formation”; (2) f<strong>in</strong>d<strong>in</strong>g<br />
<strong>the</strong> realizers for <strong>the</strong> causal-functional role – <strong>in</strong> this case,<br />
DNA molecules; <strong>and</strong> (3) a <strong>the</strong>ory – <strong>in</strong> our case molecular<br />
biology – that expla<strong>in</strong>s how <strong>the</strong> realizers – <strong>the</strong> DNA molecules<br />
– fulfil this role (Kim 2005, 101). In <strong>the</strong> m<strong>in</strong>d-body<br />
case, <strong>the</strong> higher-level properties <strong>in</strong> question are such as<br />
“be<strong>in</strong>g <strong>in</strong> a mental state S”.<br />
Although Kim’s notion of reduction through<br />
functional def<strong>in</strong>ition is not, by any means, <strong>the</strong> only<br />
<strong>in</strong>telligible concept of reduction, I will make it <strong>the</strong> target of<br />
my follow<strong>in</strong>g discussion on reductionism. In <strong>the</strong> end of this<br />
paper I will <strong>in</strong>clude a very brief comment on <strong>the</strong>ory<br />
reduction <strong>and</strong> reduction through m<strong>in</strong>d-body identity. There<br />
are a few th<strong>in</strong>gs to notice about this reduction schema.<br />
First, <strong>the</strong> functional def<strong>in</strong>ition should, of course, be<br />
adequate to <strong>the</strong> established mean<strong>in</strong>g of <strong>the</strong> higher-level<br />
concept. It is sometimes said that, because of some<br />
<strong>in</strong>def<strong>in</strong>iteness of everyday-language concepts, <strong>the</strong>y can<br />
not, strictly speak<strong>in</strong>g, be def<strong>in</strong>ed. S<strong>in</strong>ce this is obviously<br />
not <strong>the</strong> real issue between reductionists <strong>and</strong> nonreductionists,<br />
‘def<strong>in</strong>ition’ here should be understood <strong>in</strong> a<br />
relaxed sense, mean<strong>in</strong>g someth<strong>in</strong>g like “rough<br />
characterization”. Second, it is <strong>the</strong> atta<strong>in</strong>ability of <strong>the</strong><br />
functional def<strong>in</strong>ition <strong>in</strong> step 1 that is essential to <strong>the</strong><br />
philosophical issue of reductionism vs. non-reductionism. If<br />
step 1 can be completed, i.e. adequate def<strong>in</strong>itions of <strong>the</strong><br />
higher-level properties can be given through causal roles,<br />
but <strong>the</strong> reduction never<strong>the</strong>less fails <strong>in</strong> steps 2 <strong>and</strong> 3, <strong>the</strong><br />
result<strong>in</strong>g position will not be non-reductionism (at least not<br />
<strong>in</strong> <strong>the</strong> usual sense of that word), but elim<strong>in</strong>ativism (if <strong>the</strong>re<br />
are no realizers for <strong>the</strong> roles specified) 1 . Third, <strong>the</strong><br />
philosophical debate over reductionism (or at least <strong>the</strong> one<br />
I have <strong>in</strong> m<strong>in</strong>d) concerns <strong>the</strong> <strong>in</strong> pr<strong>in</strong>ciple or <strong>the</strong>oretical<br />
atta<strong>in</strong>ability of <strong>the</strong> functional def<strong>in</strong>itions, not <strong>the</strong>ir<br />
atta<strong>in</strong>ability <strong>in</strong> practice.<br />
We are now <strong>in</strong> a position to see what would<br />
constitute a conclusive argument for ei<strong>the</strong>r side <strong>in</strong> <strong>the</strong><br />
reductionism debate. The m<strong>in</strong>d-body reductionist needs to<br />
show that<br />
MBR 2 It is <strong>in</strong> pr<strong>in</strong>ciple possible to def<strong>in</strong>e mental<br />
properties, adequately to <strong>the</strong> established mean<strong>in</strong>g<br />
of <strong>the</strong> concepts <strong>in</strong> question, with recourse to causalfunctional<br />
roles, not us<strong>in</strong>g mental property concepts<br />
<strong>in</strong> <strong>the</strong> def<strong>in</strong>iens.<br />
The non-reductionist, respectively, needs to show that<br />
MBR is not true, i.e. that it is not possible, even <strong>in</strong> pr<strong>in</strong>ciple,<br />
to give such def<strong>in</strong>itions.<br />
Accord<strong>in</strong>g to Kim, functional def<strong>in</strong>itions are not<br />
atta<strong>in</strong>able for concepts of phenomenal properties, but are<br />
atta<strong>in</strong>able for concepts of <strong>in</strong>tentional/cognitive properties,<br />
such as believ<strong>in</strong>g that p or desir<strong>in</strong>g that q (Kim 2005). I will<br />
argue that functional def<strong>in</strong>itions are not atta<strong>in</strong>able <strong>in</strong> <strong>the</strong><br />
case of <strong>in</strong>tentional properties ei<strong>the</strong>r, that is, that MBR does<br />
not hold for <strong>in</strong>tentional properties.<br />
2. The Normativity Argument<br />
My argument is based on <strong>the</strong> discussion on rule-follow<strong>in</strong>g<br />
<strong>in</strong> Saul Kripke’s Wittgenste<strong>in</strong> on Rules <strong>and</strong> Private Language<br />
(Kripke 1982). Kripke’s question was, approximately,<br />
“what makes it <strong>the</strong> case that, <strong>in</strong> say<strong>in</strong>g ‘plus’ <strong>and</strong><br />
us<strong>in</strong>g <strong>the</strong> + symbol, I mean addition <strong>and</strong> not some o<strong>the</strong>r<br />
function?” His answer was, roughly, that <strong>the</strong>re is noth<strong>in</strong>g,<br />
no fact, short of <strong>the</strong> whole practices of attribut<strong>in</strong>g mean<strong>in</strong>gs<br />
<strong>and</strong> do<strong>in</strong>g addition <strong>in</strong> <strong>the</strong> community of languageusers<br />
that makes <strong>the</strong> difference between my mean<strong>in</strong>g <strong>the</strong><br />
one th<strong>in</strong>g or <strong>the</strong> o<strong>the</strong>r. Kripke specially considers one sort<br />
of facts that might be thought to make <strong>the</strong> difference.<br />
Namely, facts about my dispositions to use <strong>the</strong> word ‘plus’<br />
<strong>and</strong> <strong>the</strong> + symbol. Now <strong>the</strong>se dispositions are exactly <strong>the</strong><br />
k<strong>in</strong>d of causal-functional roles that appear <strong>in</strong> Kim-style<br />
reductive explanations. Fur<strong>the</strong>rmore, functionally def<strong>in</strong><strong>in</strong>g<br />
1 That is, if we have conclusive grounds for claim<strong>in</strong>g that <strong>the</strong>re are no realizers<br />
for <strong>the</strong> causal roles. If we have just not yet managed to f<strong>in</strong>d <strong>the</strong> right realizers,<br />
<strong>the</strong>n, of course, we do not have to give <strong>in</strong> to elim<strong>in</strong>ativism.<br />
2 For m<strong>in</strong>d-body reductionism.