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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176<br />
“Downward Causation”: Emergent, Reducible or Non-Existent? — Peter P. Kirschenmann<br />
mechanics, hold<strong>in</strong>g for <strong>the</strong> wheel, need not be considered<br />
as emergent, as <strong>the</strong>y equally hold for <strong>the</strong> free movement<br />
of molecules or stable collections <strong>the</strong>reof.<br />
There are many more macroscopic, structurally<br />
emergent properties, like fluidity, viscosity, solidity which<br />
can be analyzed <strong>in</strong> a correspond<strong>in</strong>g manner.<br />
A quite different, well-worn example is <strong>the</strong> Bénard<br />
<strong>in</strong>stability. It concerns an open system, a fluid heated from<br />
below, far from <strong>the</strong>rmodynamical equilibrium. At a critical<br />
temperature difference between bottom <strong>and</strong> top, heat<br />
conduction changes <strong>in</strong>to convection, <strong>in</strong> <strong>the</strong> form of<br />
cyl<strong>in</strong>drical rolls, with <strong>the</strong> top closed, or <strong>in</strong> that of Bénard<br />
cells, with <strong>the</strong> top open. These patterns of movement are<br />
emergent <strong>in</strong> a sense that goes beyond structural<br />
emergence. Some say (cf. Rockwell 1998) that such a<br />
pattern is created by <strong>the</strong> coord<strong>in</strong>ation of <strong>the</strong> motions of<br />
molecules, which <strong>in</strong> turn, “downwardly”, <strong>in</strong>fluences <strong>the</strong>ir<br />
behavior, <strong>and</strong> call this a case of ‘circular causality’.<br />
Yet, <strong>the</strong>re is at best some downward determ<strong>in</strong>ation:<br />
groups of molecules, tend<strong>in</strong>g to move (first) upwards, are<br />
coax<strong>in</strong>g, <strong>and</strong> are be<strong>in</strong>g coaxed by, neighbor<strong>in</strong>g molecules<br />
<strong>in</strong>to <strong>the</strong> emerg<strong>in</strong>g motion pattern <strong>and</strong> kept <strong>in</strong> it. As<br />
possibility <strong>and</strong> actuality, this pattern is a determ<strong>in</strong><strong>in</strong>g<br />
circumstance, though not an extra force. One should not<br />
say that <strong>the</strong> “system as a whole” does much <strong>in</strong> determ<strong>in</strong><strong>in</strong>g<br />
<strong>the</strong> behavior of its “parts”, s<strong>in</strong>ce <strong>the</strong> decisive, but “outside”,<br />
driv<strong>in</strong>g forces are <strong>the</strong> heat flow <strong>and</strong> gravity, act<strong>in</strong>g under<br />
<strong>the</strong> geometrical conditions of <strong>the</strong> pan of fluid <strong>and</strong> <strong>the</strong><br />
possible motions of <strong>the</strong> molecules. A hard-headed<br />
reductionist might want to take <strong>the</strong> system plus total<br />
environment as <strong>the</strong> real “whole” to be analyzed <strong>in</strong> terms of<br />
processes of <strong>the</strong>ir micro-constituents.<br />
The cyl<strong>in</strong>drical rolls can ei<strong>the</strong>r turn clockwise or<br />
counterclockwise. There is a “bifurcation po<strong>in</strong>t”: it is up to<br />
chance which way <strong>the</strong>y turn. This spontaneous,<br />
unpredictable “choice”, at <strong>the</strong> po<strong>in</strong>t of <strong>in</strong>stability, can be<br />
taken to enhance <strong>the</strong> emergent character of <strong>the</strong> result<strong>in</strong>g<br />
pattern.<br />
What about <strong>the</strong> pattern be<strong>in</strong>g a significant factor at<br />
its “own level” of macroscopic causality? It is responsible<br />
for <strong>the</strong> rapid heat flow; it can be photographed <strong>and</strong> pr<strong>in</strong>ted<br />
as illustration.<br />
The Bénard <strong>in</strong>stability represents a nonl<strong>in</strong>ear<br />
dynamic system. The emergence of <strong>the</strong> patterns<br />
constitutes a symmetry break. Such systems are<br />
dissipative structures, s<strong>in</strong>ce energy is not conserved with<strong>in</strong><br />
<strong>the</strong>m. They also count as examples of “self-organization”,<br />
mostly a misnomer, <strong>in</strong>asmuch as <strong>the</strong> driv<strong>in</strong>g forces are<br />
heteronomous. The behavior of nonl<strong>in</strong>ear dynamic<br />
systems can lie <strong>in</strong> chaotic regimes, but also <strong>in</strong> regimes<br />
represent<strong>in</strong>g various k<strong>in</strong>ds of “attractors”, comparable to<br />
<strong>the</strong> patterns <strong>in</strong> Bénard cells.<br />
Organisms also are open systems, but differ from<br />
such non-liv<strong>in</strong>g examples by <strong>the</strong>ir enormous degree of<br />
<strong>in</strong>ternal regulation, coord<strong>in</strong>ation <strong>and</strong> <strong>in</strong>tegration of all <strong>the</strong>ir<br />
constituent processes. They possess emergent features,<br />
such as multiplication, growth, self-repair etc., which are<br />
determ<strong>in</strong><strong>in</strong>g factors <strong>in</strong> all k<strong>in</strong>ds of causal relationships, as<br />
when we catch a cold or when moles disfigure our lawns.<br />
Yet, I will not discuss claims that <strong>the</strong>ir lives might manifest<br />
a special k<strong>in</strong>d of “downward causation” <strong>and</strong> turn to more<br />
abstract considerations.<br />
4. Supervenience <strong>and</strong> Critique<br />
A decisive argument for emergent properties is <strong>the</strong> multiple<br />
realizability argument. The st<strong>and</strong>ard example is <strong>the</strong> mental<br />
state of be<strong>in</strong>g <strong>in</strong> pa<strong>in</strong>, which can be realized by different<br />
physical states <strong>in</strong> <strong>the</strong> same or different persons. This provides<br />
an argument aga<strong>in</strong>st (type) identity <strong>the</strong>ories of m<strong>in</strong>d<br />
<strong>and</strong> bra<strong>in</strong>, reductive or elim<strong>in</strong>ative accounts of <strong>the</strong> m<strong>in</strong>d<br />
<strong>and</strong> for <strong>the</strong> now widespread view of “non-reductive physicalism”.<br />
Similarly, biological functions can be physically<br />
realized <strong>in</strong> different ways <strong>in</strong> different organisms.<br />
The discussion of <strong>the</strong> relation between properties at<br />
different “levels” has been dom<strong>in</strong>ated by <strong>the</strong> ra<strong>the</strong>r formal<br />
notion of supervenience, which accommodates <strong>the</strong> general<br />
idea of multiple realizability, but is chiefly used <strong>in</strong> <strong>the</strong><br />
philosophy of m<strong>in</strong>d.<br />
One def<strong>in</strong>ition is: “A set of properties A supervenes<br />
upon ano<strong>the</strong>r set B just <strong>in</strong> case no two th<strong>in</strong>gs can differ<br />
with respect to A-properties without also differ<strong>in</strong>g with<br />
respect to <strong>the</strong>ir B-properties.” (McLaughl<strong>in</strong>, Bennett 2005).<br />
It states a dependency, not fur<strong>the</strong>r specified. Important<br />
versions of <strong>the</strong> notion differ <strong>in</strong> <strong>the</strong> k<strong>in</strong>d of necessity<br />
attributed to this dependency.<br />
Jaegwon Kim, a prime elaborator of <strong>the</strong> notion, used<br />
it <strong>in</strong> his “causal exclusion argument” aga<strong>in</strong>st “downward<br />
causation”, or, to show that “non-reductive physicalism” is<br />
self-contradictory (cf. Rockwell 1998). Consider <strong>the</strong><br />
follow<strong>in</strong>g schema:<br />
M causes M*<br />
P causes P*<br />
Here, a mental event (<strong>in</strong>stantiation of, or change <strong>in</strong>, a mental<br />
property) M is assumed as caus<strong>in</strong>g ano<strong>the</strong>r mental<br />
event M*. Yet, M supervenes on (is realized by) a physical<br />
(neurophysiologic) event P, which causes P*, <strong>the</strong> physical<br />
realization of M*. Kim argued, put simply, that <strong>the</strong> mental<br />
layer would do no causal work: P causes P* all by itself; M<br />
<strong>in</strong> no way “downwardly causes” P*; <strong>the</strong> mental layer is at<br />
best epiphenomenal, if not non-existent.<br />
In its strongest form, <strong>the</strong> argument presupposes <strong>the</strong><br />
“causal closure” of <strong>the</strong> physical world. Yet, if this was just<br />
<strong>the</strong> world of <strong>the</strong> most fundamental physical entities, <strong>the</strong>n<br />
everyth<strong>in</strong>g else, not just <strong>the</strong> mental realm, would be<br />
epiphenomenal. The argument also assumes causation to<br />
be <strong>the</strong> only k<strong>in</strong>d of determ<strong>in</strong>ation.<br />
What <strong>the</strong> supervenience approach totally ignores,<br />
as Mark Bickhard with Donald Campbell (2000) rightly<br />
po<strong>in</strong>ted out, are <strong>the</strong> external relations of <strong>the</strong> systems<br />
concerned, which, as we saw, are especially important <strong>in</strong><br />
<strong>the</strong> case of open systems. More generally, <strong>the</strong>y criticize it<br />
for still assum<strong>in</strong>g a basic level of fundamental particles,<br />
thus a metaphysics of substances, whereas modern<br />
physics forces us to adopt a metaphysics of fields. Fields<br />
are cont<strong>in</strong>uously <strong>in</strong> process, which is “<strong>in</strong>herently <strong>and</strong><br />
necessarily organized” or patterned. “So, delegitimat<strong>in</strong>g<br />
process organization as a potential locus of emergence<br />
renders all reality epiphenomenal”. This absurdity amounts<br />
to an argument for <strong>the</strong> reality of all patterns of processes,<br />
also for <strong>the</strong> plausibility of <strong>the</strong> emergent reality of m<strong>in</strong>d.<br />
Non-trivial emergence, for <strong>the</strong> authors, is “emergent<br />
(novel) causality”, which (<strong>in</strong> contrast to my view) will, thus<br />
as a criterion, “necessarily <strong>in</strong>volve downward causality”.<br />
Unfortunately, <strong>the</strong>y fail to articulate some alternative notion<br />
of pattern causality. The k<strong>in</strong>ds of “downward causation”<br />
<strong>the</strong>y survey are all cases of constra<strong>in</strong>ts, thus at best cases<br />
of “downward” determ<strong>in</strong>ation.