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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“Downward Causation”: Emergent, Reducible or Non-Existent?<br />
Peter P. Kirschenmann, Amsterdam, The Ne<strong>the</strong>rl<strong>and</strong>s<br />
1. Introduction<br />
It is common to view reality as a hierarchy of levels, such<br />
as <strong>the</strong> physical, biological, psychological level. Entities<br />
(plus <strong>the</strong>ir properties) at higher levels (of “organization” or<br />
“complexity”) consist of entities of lower levels, but are<br />
supposed to be “emergent” – form “wholes that are more<br />
than <strong>the</strong> sum of <strong>the</strong>ir parts” – <strong>and</strong>, possibly, have “downward<br />
causal” <strong>in</strong>fluences on <strong>the</strong>ir parts.<br />
All <strong>the</strong>se views, often not well-articulated, are<br />
contested. For hard-headed (elim<strong>in</strong>ative) materialists or<br />
physicalists, <strong>the</strong>re is no emergence, let alone “downward<br />
causation”. For reductionists, <strong>the</strong>y are “noth<strong>in</strong>g but”<br />
material processes. Emergentists often rest content with<br />
argu<strong>in</strong>g for <strong>the</strong>ir possibility. “Non-reductive physicalists”<br />
recognize emergent phenomena, but <strong>in</strong>sist on <strong>the</strong>ir be<strong>in</strong>g<br />
physically based.<br />
I myself th<strong>in</strong>k that <strong>the</strong> occurrence of a hawk catch<strong>in</strong>g<br />
a mouse is a macroscopic emergent phenomenon, though<br />
I doubt that it <strong>in</strong>volves “downward causation”. I used to be<br />
a fan of layered ontologies (e.g. Nicolai Hartmann’s). Yet<br />
lately, I th<strong>in</strong>k that we should avoid as much as possible<br />
impos<strong>in</strong>g a level structure on reality. Surely, a dist<strong>in</strong>ction<br />
between macrolevel <strong>and</strong> microlevel often is very sensible,<br />
but it can misfire.<br />
I shall discuss two orig<strong>in</strong>al views as well as <strong>the</strong><br />
muddled conceptualization <strong>and</strong> term<strong>in</strong>ology, analyze two<br />
examples, comment on <strong>the</strong> “causal exclusion argument”,<br />
<strong>and</strong> conclude with a computer analogy.<br />
2. The Muddle of ‘Downward Causation’<br />
Donald T. Campbell, <strong>in</strong> 1974, first used <strong>the</strong> expression<br />
‘downward causation’ (cf. Hulswit 2006, 266), for <strong>the</strong> view<br />
that “all processes at <strong>the</strong> lower level of a hierarchy are<br />
restra<strong>in</strong>ed by <strong>and</strong> act <strong>in</strong> conformity to <strong>the</strong> laws of <strong>the</strong><br />
higher levels”. His (biological) hierarchy ran from molecules<br />
<strong>and</strong> cells up to populations <strong>and</strong> evolution. He noted<br />
himself that <strong>the</strong> expression was at odds with our usual<br />
concept of efficient causation: his higher-level “laws” selectively<br />
restra<strong>in</strong> lower-level processes, unlike events caus<strong>in</strong>g<br />
o<strong>the</strong>r events.<br />
Around that time, Roger W. Sperry, after his splitbra<strong>in</strong><br />
<strong>in</strong>vestigations, started defend<strong>in</strong>g his “emergent<br />
<strong>in</strong>teractionism” (cf. Emmeche et al. 2000, Ripley 1984,<br />
Hulswit 2006: 269). To clarify <strong>the</strong> “form of control” that<br />
conscious phenomena exert over neural events he used<br />
<strong>the</strong> examples of a wheel runn<strong>in</strong>g downhill <strong>and</strong> an eddy <strong>in</strong> a<br />
stream. The movement <strong>and</strong> fate of <strong>the</strong> constituent<br />
molecules are “determ<strong>in</strong>ed very largely by <strong>the</strong> holistic<br />
properties of <strong>the</strong> whole wheel” or <strong>the</strong> whole eddy, though<br />
without any change <strong>in</strong> <strong>the</strong> lower-level molecular laws.<br />
Similarly, <strong>the</strong> component parts of “an excitatory neural<br />
process are carried along <strong>and</strong> thus controlled by dynamic<br />
properties of <strong>the</strong> whole system”, namely by unitary mental<br />
experiences. Sperry was not quite happy with <strong>the</strong> term<br />
‘<strong>in</strong>teractionism’, as it smacked too much of a Cartesian<br />
dualism.<br />
What ‘downward causation’ or <strong>the</strong> downward part of<br />
‘<strong>in</strong>teraction’ is for <strong>the</strong>se authors rema<strong>in</strong>s unclear.<br />
Meanwhile, <strong>the</strong> term<strong>in</strong>ological diversity has been<br />
explod<strong>in</strong>g. Thus, <strong>the</strong> higher level has been said to cause<br />
<strong>in</strong>asmuch as it restra<strong>in</strong>s, constra<strong>in</strong>s, controls, organizes,<br />
structures, determ<strong>in</strong>es, governs, delimits, bounds,<br />
entra<strong>in</strong>s, enslaves, harnesses or selects <strong>the</strong> lower-level<br />
phenomena (cf. Hulswit 2006: 279f.), while said to emerge<br />
from, cannot be expla<strong>in</strong>ed by, reduced to, or predicted<br />
from, <strong>the</strong>m <strong>and</strong> <strong>the</strong>ir laws. S<strong>in</strong>ce several of those “causal<br />
<strong>in</strong>fluences” hardly are examples of efficient causation,<br />
some regard <strong>the</strong>m as Aristotelian formal or f<strong>in</strong>al<br />
(functional) causes. The most general <strong>and</strong> neutral term,<br />
though <strong>in</strong> need of appropriate qualifications, is<br />
‘determ<strong>in</strong>es’. Ano<strong>the</strong>r disconcert<strong>in</strong>g variation concerns <strong>the</strong><br />
relata of <strong>the</strong> alleged downward causality: entities,<br />
substances, events, processes, states, types or<br />
<strong>in</strong>stantiations of properties, patterns, structures, laws or<br />
regularities.<br />
No doubt, novel th<strong>in</strong>gs have diachronically<br />
“emerged” dur<strong>in</strong>g <strong>the</strong> evolution of <strong>the</strong> universe: stars,<br />
heavy elements, planets, life, consciousness. We focus<br />
here on synchronic emergence: “higher levels of reality” of<br />
some permanence. Crucial <strong>in</strong> identify<strong>in</strong>g emergent entities<br />
or systems, I th<strong>in</strong>k, are <strong>the</strong>ir significant, possibly lawful<br />
“horizontal” <strong>in</strong>teractions with entities at <strong>the</strong> “same level”,<br />
ra<strong>the</strong>r than “downward” <strong>in</strong>fluences.<br />
A useful dist<strong>in</strong>ction is between three possible<br />
mean<strong>in</strong>gs of ‘downward causation’ accord<strong>in</strong>g to <strong>the</strong>ir<br />
strength (cf. Hulswit 2006: 280, also Emmeche et al.<br />
2000), all concern<strong>in</strong>g an active system constituted by a set<br />
of active elements:<br />
weak – “downward explanation”: <strong>the</strong> behavior of <strong>the</strong><br />
elements cannot adequately be expla<strong>in</strong>ed without<br />
reference to <strong>the</strong> system;<br />
medium – “downward determ<strong>in</strong>ation”: it is partly determ<strong>in</strong>ed<br />
by <strong>the</strong> system;<br />
strong – “downward causation”: it is partly brought<br />
about by <strong>the</strong> system.<br />
3. Examples – Analyzed<br />
The most <strong>in</strong>trigu<strong>in</strong>g questions of emergence concern life<br />
<strong>and</strong> m<strong>in</strong>d. Yet, phenomena of <strong>the</strong> non-liv<strong>in</strong>g world have<br />
raised similar <strong>and</strong> more easily analyzable questions. They<br />
often are supposed to attest to a cont<strong>in</strong>uity of emergence<br />
<strong>and</strong> downward causation through all layers of reality (e.g.<br />
Rockwell 1998). I have my doubts.<br />
Sperry’s wheel is an example <strong>in</strong> po<strong>in</strong>t. The<br />
macroscopic properties of <strong>the</strong> wheel, toge<strong>the</strong>r with gravity,<br />
slope etc., determ<strong>in</strong>e <strong>the</strong> movement of <strong>the</strong> wheel <strong>and</strong> thus<br />
a fortiori that of its constituent molecules. Its stable circular<br />
shape, due to <strong>the</strong> cohesive arrangement of its<br />
constituents, is an emergent property – for not be<strong>in</strong>g a<br />
property of <strong>the</strong> constituents – <strong>in</strong> an <strong>in</strong>nocent sense, a<br />
“structural emergence. It can thus be “expla<strong>in</strong>ed”, without<br />
gett<strong>in</strong>g reduced to properties <strong>and</strong> arrangement of<br />
molecules. It is a factor <strong>in</strong> macroscopic causal relations, as<br />
when <strong>the</strong> wheel should bump <strong>in</strong>to a wall. Yet, pace Sperry,<br />
<strong>the</strong>re is no “<strong>in</strong>teraction” between <strong>the</strong> wheel as a whole <strong>and</strong><br />
its constituents, let alone its “downwardly caus<strong>in</strong>g” <strong>the</strong>ir<br />
movement, except <strong>in</strong> <strong>the</strong> weak sense of downward<br />
explanation. Note, pace Campbell, that <strong>the</strong> laws of<br />
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