E.J. Lowe - Causal Closure Principles and emergentism.pdf

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Causal Closure Principles and
E . J. L O WE
At one time, it was popular to argue against interactionist dualism
by appeal to the conservation laws of physics, such as the laws of the
conservation of energy and momentum. However, those laws are
not sacrosanct and there need be nothing unscientific about ques-
tioning them—indeed they have been questioned from time to time
by cosmologists and other physicists. Think, for instance, of Bondi
and Gold’s steady-state model of the universe, which postulated the
continuous creation of matter and hence of energy. 1 In an y case,
appeal to those laws can at best only be used to attack dualist mod-
els of psychophysical causation which attribute to the non-physical
mind an ability to affect the energy or momentum of a physical sys-
tem. I say ‘at best’ because some interactionist dualists, such as W.
D. Hart, have postulated the existence of ‘psychic energy’, which is
convertible into physical energy in accordance with the conservation
laws. 2 It w on’t do simply to object that energy is by definition a
physical quantity, as this threatens to turn the dispute into a purely
verbal one. In view of these and other limitations, it would serve
physicalists well if they could frame a more general argument
against interactionist dualism, which did not make specific appeal to
the conservation laws. 3 Man y modern physicalists think that they
have an argument of just this sort to hand, in the form of the causal
closure argument . 4
In fact, this is not so much a single argument as a family of argu-
ments. A ‘causal closure argument’, as I shall be interpreting that
1 See H. Bondi, Cosmology , 2nd edn (Cambridge University Press,
1961), Ch. XII.
2 See W. D. Hart, The Engines of the Soul (Cambridge University Press,
1988), Ch. 9.
3 F or further discussion of the (ir)relevance of physical conservation
laws to the problem of psychophysical causation, see my Subjects of
Experience (Cambridge University Press, 1996), pp. 56–63.
4 A r elatively early version of this form of argument may be found in
Christopher Peacocke, Holistic Explanation: Action, Space, Interpretation
(Oxford: Clarendon Press, 1979), pp. 134–43, though Peacocke’s version
does not exactly conform to the pattern I specify below. I raise an objec-
tion to Peacocke’s argument in my ‘Against an Argument for Token
Identity’, Mind 90 (1981), pp. 120–1.
Philosophy 75 2000
E. J. Lowe
phrase, has three premises: first, a physical causal closure principle;
second, the claim—to which interactionist dualists are themselves
committed—that at least some mental events are causes of physical
events; and third, the claim that the physical effects of mental caus-
es are not, in general, causally overdetermined. 5 T he conclusion of
such an argument is that at least some mental events are identical
with physical events. Incidentally, I am assuming for the time being
that the relata of causal relations are events, broadly conceived to
include both processes and states, but not too much turns on this
assumption at the moment. Later on, however, I shall introduce a
distinction between event-causation and fact-causation which may
have a significant bearing on the issues under discussion. 6
As we shall see shortly, physicalists espousing causal closure argu-
ments do not always agree on the way to formulate their causal clo-
sure principles. What is crucial to the success of such an argument
is that the causal closure principle appealed to should be neither too
strong nor too weak. If the principle is so strong, for instance, as to
render redundant the third premise of the argument—the non-
overdetermination claim—then the argument will become simply
question-begging, because it will amount to an argument from two
premises, one of which is accepted by the dualist, to a conclusion
which is not accepted by the dualist: and in these circumstances the
dualist may justly urge that his opponent is, in effect, merely assert-
ing what he is denying. Moreover, to have any persuasive force, the
causal closure principle must be one for which some measure of
empirical support can plausibly be mustered, and this places limits
on how strong it can be. On the other hand, the causal closure prin-
ciple must, obviously, not be so weak that the argument in which it
is deployed turns out to be invalid. What I shall try to show in this
paper is that it is in fact very difficult, if not impossible, for the
physicalist to formulate a causal closure principle which is neither
too strong nor too weak by these standards. In particular, I shall
argue that there are various forms of naturalistic dualism, of an
emergentist character, which are perfectly consistent with the
5 W hy should systematic causal overdetermination be ruled out where
psychophysical causation is concerned? Perhaps it shouldn’t be, and this
would be a quick way to dispose of causal closure arguments: see further
Eugene Mills, ‘Interactionism and Ove rd e t e r m i n a t i o n’, A m e r i c a n
Philosophical Quarterly 33 (1996), pp. 105–17. But I take it that most inter-
actionist dualists would not wish to resort to this strategy if possible, as it
looks suspiciously ad hoc .
6 For more on the distinction between event-causation and fact-causa-
tion, see Jonathan Bennett, Events and their Names (Oxford: Clarendon
Press, 1988), pp. 21ff.
Causal Closure Principles and Emer
strongest physical causal closure principles that can plausibly be
advocated. If that is correct, then it means that causal closure argu-
ments against interactionist dualism do not, after all, provide a
superior alternative to the discredited arguments which appeal to
the conservation laws of physics.
I mentioned a moment ago the variety of causal closure principles
appealed to by physicalists. Let me briefly illustrate this variety by
some examples. In a recent paper, David Papineau appeals to the
following principle, which he calls the principle of ‘the complete-
ness of physics’: 7
(1A) All physical effects have sufficient physical causes.
But in an earlier book, he appeals instead to a somewhat different
principle, which he calls by the same title, namely: 8
(1B) All physical effects have complete physical causes.
Papineau explains that by ‘complete’ here he means ‘“complete” in
the sense that those causes on their own suffice by physical law to
fix the chances of those effects’. However, he does also advert to the
latter formulation in a footnote to the more recent paper, remarking
that ‘a stricter version ... would say that the chances of physical
effects are always fixed by sufficient physical causes’. 9
In another recent contribution to the literature on causal closure,
Scott Sturgeon states what he too calls the principle of the com-
pleteness of physics as follows: 10
(1C) Every physical effect has a fully revealing, purely physical
However, Sturgeon himself glosses this in terms reminiscent of
Papineau’s, as meaning that ‘physical effects have their chances fully
determined by physical events alone’. In a paper commenting on
Sturgeon’s, Paul Noordhof seizes upon this gloss, remarking that it
‘seems more perspicuous’ than Sturgeon’s official formulation. 11
7 David Papineau, ‘Mind the Gap’, in J ames E. Tomberlin (ed.),
Philosophical Perspectives , 12: Language, Mind and Ontology (Oxford:
Blackwell, 1998), pp. 373–88: see p. 375.
8 David Papineau, Philosophical Naturalism (Oxford: Blackwell, 1993),
p. 22.
9 Papineau, ‘Mind the Gap’, p. 386, n. 4.
10 Scott Stur geon, ‘Physicalism and Overdetermination’, Mind 107
(1998), pp. 411–32: see p. 413.
1 1 Paul Noord h o f, ‘The Ove rdetermination Argument ve rsus the
Cause-and-Essence Principle—No Contest’, M i n d 108 (1999), pp.
367–75: see p. 367.
E. J. Lowe
Accordingly, Noordhof advances the following as his own preferred
version of the causal closure principle:
(1D) Every physical effect has its chance fully determined by
physical events alone.
It is worth mentioning, however, that in a further gloss on his ver-
sion of the principle, Sturgeon asserts that ‘physics does not admit
that physical effects have non-physical causes’, 12 and this suggests
yet another formulation, namely:
(1E) No physical effect has a non-physical cause.
Pretty clearly, principles (1A) to (1E) are not all equivalent to one
another, whatever one makes of the various glosses supplied by their
advocates. And these by no means exhaust the variety of formula-
tions to be found in the literature. One might have hoped for more
exactitude and agreement amongst physicalists when it comes to the
formulation of a principle so central to their position.
One thing we should notice immediately is that the last version
just cited, (1E), is too strong by the standards laid down earlier,
because it is bound to render redundant the non-overdetermination
premise of any causal closure argument in which it is deployed. To
see this clearly, let me now state explicitly what the remaining
premises and the conclusion of such an argument are supposed to
be. Obviously, these premises and the conclusion are themselves
susceptible to some variation in their formulation, but I shall utilize
what I hope can be agreed to be uncontentious versions of them.
The second premise, maintaining the existence of psychophysical
causation, may be stated thus:
(2) At least some mental events are causes of physical events.
The third premise, excluding the possibility of systematic causal
overdetermination, may be expressed as follows:
(3) The physical effects of
mental causes are not, in general,
c a u s a l l y overdetermined.
And the anti-dualist conclusion of the argument is supposed to be
(4) At least some mental events are identical with physical events.
However, it is quite evident that (1E) and (2) together entail (4),
without the help of (3), so that (1E) can fairly be dismissed by the
interactionist dualist as question-begging—as I am sure it would be.
12 Stur geon, ‘Physicalism and Overdetermination’, p. 413.
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