Reduction and Elimination in Philosophy and the Sciences

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“Downward Causation”: Emergent, Reducible or Non-Existent? — Peter P. Kirschenmann
mechanics, holding for the wheel, need not be considered
as emergent, as they equally hold for the free movement
of molecules or stable collections thereof.
There are many more macroscopic, structurally
emergent properties, like fluidity, viscosity, solidity which
can be analyzed in a corresponding manner.
A quite different, well-worn example is the Bénard
instability. It concerns an open system, a fluid heated from
below, far from thermodynamical equilibrium. At a critical
temperature difference between bottom and top, heat
conduction changes into convection, in the form of
cylindrical rolls, with the top closed, or in that of Bénard
cells, with the top open. These patterns of movement are
emergent in a sense that goes beyond structural
emergence. Some say (cf. Rockwell 1998) that such a
pattern is created by the coordination of the motions of
molecules, which in turn, “downwardly”, influences their
behavior, and call this a case of ‘circular causality’.
Yet, there is at best some downward determination:
groups of molecules, tending to move (first) upwards, are
coaxing, and are being coaxed by, neighboring molecules
into the emerging motion pattern and kept in it. As
possibility and actuality, this pattern is a determining
circumstance, though not an extra force. One should not
say that the “system as a whole” does much in determining
the behavior of its “parts”, since the decisive, but “outside”,
driving forces are the heat flow and gravity, acting under
the geometrical conditions of the pan of fluid and the
possible motions of the molecules. A hard-headed
reductionist might want to take the system plus total
environment as the real “whole” to be analyzed in terms of
processes of their micro-constituents.
The cylindrical rolls can either turn clockwise or
counterclockwise. There is a “bifurcation point”: it is up to
chance which way they turn. This spontaneous,
unpredictable “choice”, at the point of instability, can be
taken to enhance the emergent character of the resulting
pattern.
What about the pattern being a significant factor at
its “own level” of macroscopic causality? It is responsible
for the rapid heat flow; it can be photographed and printed
as illustration.
The Bénard instability represents a nonlinear
dynamic system. The emergence of the patterns
constitutes a symmetry break. Such systems are
dissipative structures, since energy is not conserved within
them. They also count as examples of “self-organization”,
mostly a misnomer, inasmuch as the driving forces are
heteronomous. The behavior of nonlinear dynamic
systems can lie in chaotic regimes, but also in regimes
representing various kinds of “attractors”, comparable to
the patterns in Bénard cells.
Organisms also are open systems, but differ from
such non-living examples by their enormous degree of
internal regulation, coordination and integration of all their
constituent processes. They possess emergent features,
such as multiplication, growth, self-repair etc., which are
determining factors in all kinds of causal relationships, as
when we catch a cold or when moles disfigure our lawns.
Yet, I will not discuss claims that their lives might manifest
a special kind of “downward causation” and turn to more
abstract considerations.
4. Supervenience and Critique
A decisive argument for emergent properties is the multiple
realizability argument. The standard example is the mental
state of being in pain, which can be realized by different
physical states in the same or different persons. This provides
an argument against (type) identity theories of mind
and brain, reductive or eliminative accounts of the mind
and for the now widespread view of “non-reductive physicalism”.
Similarly, biological functions can be physically
realized in different ways in different organisms.
The discussion of the relation between properties at
different “levels” has been dominated by the rather formal
notion of supervenience, which accommodates the general
idea of multiple realizability, but is chiefly used in the
philosophy of mind.
One definition is: “A set of properties A supervenes
upon another set B just in case no two things can differ
with respect to A-properties without also differing with
respect to their B-properties.” (McLaughlin, Bennett 2005).
It states a dependency, not further specified. Important
versions of the notion differ in the kind of necessity
attributed to this dependency.
Jaegwon Kim, a prime elaborator of the notion, used
it in his “causal exclusion argument” against “downward
causation”, or, to show that “non-reductive physicalism” is
self-contradictory (cf. Rockwell 1998). Consider the
following schema:
M causes M*
P causes P*
Here, a mental event (instantiation of, or change in, a mental
property) M is assumed as causing another mental
event M*. Yet, M supervenes on (is realized by) a physical
(neurophysiologic) event P, which causes P*, the physical
realization of M*. Kim argued, put simply, that the mental
layer would do no causal work: P causes P* all by itself; M
in no way “downwardly causes” P*; the mental layer is at
best epiphenomenal, if not non-existent.
In its strongest form, the argument presupposes the
“causal closure” of the physical world. Yet, if this was just
the world of the most fundamental physical entities, then
everything else, not just the mental realm, would be
epiphenomenal. The argument also assumes causation to
be the only kind of determination.
What the supervenience approach totally ignores,
as Mark Bickhard with Donald Campbell (2000) rightly
pointed out, are the external relations of the systems
concerned, which, as we saw, are especially important in
the case of open systems. More generally, they criticize it
for still assuming a basic level of fundamental particles,
thus a metaphysics of substances, whereas modern
physics forces us to adopt a metaphysics of fields. Fields
are continuously in process, which is “inherently and
necessarily organized” or patterned. “So, delegitimating
process organization as a potential locus of emergence
renders all reality epiphenomenal”. This absurdity amounts
to an argument for the reality of all patterns of processes,
also for the plausibility of the emergent reality of mind.
Non-trivial emergence, for the authors, is “emergent
(novel) causality”, which (in contrast to my view) will, thus
as a criterion, “necessarily involve downward causality”.
Unfortunately, they fail to articulate some alternative notion
of pattern causality. The kinds of “downward causation”
they survey are all cases of constraints, thus at best cases
of “downward” determination.