when it was suggested that moral properties supervene on natural
properties and that our mental characteristics supervene on our
physical characteristics such as the properties of our nervous system.
The term can be defined as follows. For two sets of properties, A (the
supervenient set) and B (the subvenient set or supervenience base), A
supervenes on B just in case there can be no difference in A without a
difference in B. Turning this principle on its head gives us the
converse concept of determination: B determines A just in case
sameness with respect to B implies sameness with respect to A.
Supervenience and determination are simply two sides of the same coin.
From the basic definition initially presented, supervenience might
seem a fairly innocuous principle, yet it has led a somewhat murky and
controversial existence: some love it; some hate it. It was, for
example, described by John Post as an "accordion word: indefinitely
stretchable" (1984, p. 163). It has certainly been pulled about
throughout its history, but it does have its limits. Indeed, others
view it as too limited to be of any philosophical worth whatsoever.
This article charts the history of the concept of supervenience,
discusses the current panoply of definitions, and reviews some of the
more tractable portions of the contemporary debate. The primary aim is
to gain a feel for the basic concept without getting bogged down with
the more formal and abstruse aspects of supervenience. The aim of this
first section is to get to grips with the core idea of supervenience,
and see some of the contexts in which it has been and might be used.
1. Getting to Grips with Supervenience
As David Lewis puts it, "We have supervenience when there could be no
difference of one sort without differences of another sort" (1986, p.
14). For example: no difference in an individual's mental
characteristics without some difference in physical characteristics;
no difference in a computer's program without a difference in the
computer's circuitry; no difference in the economy without some
difference in the behavior of its underlying economic agents; no
difference in the temperature of a gas without some difference in the
behavior of the molecules forming it, and so on. But notice that there
can be differences in the neurons, circuitry, agents, and molecules
without a difference in mental, computational, economic, and thermal
properties.
The idea in each of the above cases is that some property A (or family
of properties) is "determined" by some other properties B that do not
themselves possess the property A, and that do not reduce to B (though
this is a controversial point, as we shall see): individual neurons
don't possess mental characteristics; circuits don't possess
computational properties; individual agents don't possess economic
properties; and individual molecules don't have temperatures. The
intent is to avoid the stronger relations (such as identity or
definability) between the types of property, generally because it
often isn't clear how there could be such strong relations holding
them together. Part of the reason for this, and one prime motivation
for supervenience, is that mental, computational, economic, and
thermodynamic characteristics are "multiply realizable:: the same
properties might be realized by very different underlying physical
configurations or stuff. However, it needs to be strong enough to
support a kind of non-symmetric dependence between two levels of
property, such that a "lower" level determines a "higher" level. This
feature may give rise to the notion of "levels of dependence" and, in
certain cases, "hierarchical organization": the mental is at a higher
"level," is higher up the hierarchy, from the physical; the economy is
at a higher level than the economic agents, and so on.
This hierarchy of levels charts out a progression of ontological
dependence too: without the physical stuff of neurons, circuits,
people, and molecules (or something like them), the higher level
states would not exist at all. This feature thus makes supervenience a
useful tool in analyzing relations between the subject matter of
distinct theoretical disciplines, such as the relation between physics
and biology. It is, more generally useful in analyzing relations
between things that are connected (correlated) in a way that doesn't
suggest reduction or identity. However, note that levels are not a
generic feature of supervenience. Consider the case of the
relationship between the length of the sides of a square and the area
of the square. There is, in both directions, no difference in one
without a difference in the other, and once the sides (respectively,
area) are fixed the area (respectively, length) is fixed. So we have a
clear case of supervenience. But this is a symmetric case, and so the
notion of a level of dependence or hierarchy makes no sense; it only
makes sense when the relation is asymmetric, and these make for the
most philosophically interesting cases.
But, before we get bogged down with such details, what is the basic
idea of supervenience? It is perhaps best understood by means of a
colorful example. To this end, let us begin by adapting a simple story
presented by Paul Teller (1983). Teller asks us to imagine a bunch of
watches churned out of an assembly line in the same state, so that
they are functionally and qualitatively (at least, in terms of their
intrinsic properties) identical—clearly the watches will register the
same time. The properties having to do with the physical makeup of the
watches—their structure and composition, and so on—give us our B set
of properties (the subvenient set). The supervenient A set has to do
with the time-keeping properties of the watches—for example, whether
they enable their owners to get into work on time, and so on. In this
case, as Teller points out, the A properties of some particular watch
will be the same as any other watch from the assembly line since they
have the same physical makeup (B properties), and that is all that
counts towards the A properties in this story. Being a good timekeeper
supervenes on the physical makeup of the timekeeping device: one could
not alter the time-keeping properties of the watches without altering
their underlying structural and compositional properties. Moreover,
any two devices that share their physical makeup will either both be
good or both be bad timekeepers. That is to say, the physical make-up
of a watch determines its time-keeping properties.
Though this captures much of the basic idea as encapsulated in our
opening definition (which we can abbreviate to "no A-difference
without a B-difference"), it misses one very crucial detail: modal
impact. Supervenience is not intended to be a contingent "matter of
actual fact" claim concerning two sets of properties that happen to be
correlated at some particular time or place. Rather, it is intended to
cover any situation involving A and B, covering any time, place, and
world—though there will be natural restrictions concerning which
worlds are to be included here (for example, logically possible [so
that all logically coherent, non-contradictory worlds are considered],
nomologically possible [so that all worlds permitted by the laws of
physics are considered], and metaphysically possible [considering a
class of worlds somewhere between the logically possible and the
nomologically possible ones]). Different restrictions give different
strengths. In our example, we should have to extend our story to
include all possible watches that are indistinguishable in terms of
their B-properties, including those inhabiting distinct worlds (from
alien worlds and Twin-Earths, perhaps to worlds with different laws of
physics). This additional modal aspect results in a profusion of
distinct formulations that aim to adequately capture the fundamental
notion of supervenience. Further proliferation results from the
question of what are to be the objects that have the properties that
enter into the supervenience/determination relation. Supervenience is,
then, clearly far from innocuous!
2. The Recent History of Supervenience
Jaegwon Kim (1993, p. 131) notes that the term "supervenience" was in
currency as far back as 1594. In its vernacular sense it means to
"[come upon] a given event as something additional and extraneous
(perhaps as something unexpected)" (ibid, p.132). However, the concept
of Supervenience, as a philosophical term of art, is generally
acknowledged to be traceable to G.E. Moore's work on value theory, and
from thence to R.M. Hare's work on meta-ethics in which the term
'supervenience' was introduced into the philosophical literature.
There it stifled for some time, before being unearthed by Davidson who
applied it to the 'mental-physical' relationship. Let us review some
central points from this historical development.
In "The Conception of Intrinsic Value" Moore writes that:
…if a given thing possesses any kind of intrinsic value in a
certain degree, then not only must that same thing possess it, under
all circumstances, in the same degree, but also anything exactly like
it, must, under all circumstances, possess it in exactly the same
degree. … it is not possible that of two exactly similar things one
should possess it and the other not, or that one should possess it in
one degree, and the other in a different one.
(Moore 1922, p. 261)
This sentiment is virtually parroted by Hare, this time specifically
utilizing the term "supervenience" to describe the relation between
certain natural (non-moral, physical) and moral properties, giving us
'moral supervenience':
…let us take that characteristic of "good" which has been called
its supervenience. Suppose that we say 'St. Francis was a good man.'
It is logically impossible to say this and to maintain at the same
time that there might have been another man placed exactly in the same
circumstances as St. Francis, and who behaved in exactly the same way,
but who differed from St. Francis in this respect only, that he was
not a good man.
(Hare 1952, p. 145)
Before we continue with the historical matters, let us briefly pause
to consider what this means. Again, let's give a simple example.
Imagine we draw up a pair of catalogues of the properties of two
people Saint Francis and Faint Srancis. The properties of Saint
Francis are, say, kindness, bravery, niceness, neighborliness, and
goodness. Faint Srancis' properties differ from Saint Francis only in
that the last property, goodness, is missing from his catalogue.
Suppose, instead, that he has the property "badness" in its place.
Now, according to the moral supervenience thesis espoused by Hare,
this is simply not a genuinely possible state of affairs. All of the
other properties, minus goodness, serve to fix or determine the
property of goodness. It is just not possible that there be two such
individuals differing in this way (whether they occupy the same world
or not). Therefore, in possessing all of Saint Francis' properties up
to, but not including goodness, Faint Srancis must also thereby
possess the property of goodness too. This is what is meant in saying
that the property of goodness supervenes on a family of natural
properties not including goodness. (Note that this matches
Stalnaker's, 1996, p. 87, preferred definition of supervenience: "To
say that the A-properties or facts are supervenient on the
B-properties or facts is to say that the A-facts are, in a sense,
redundant, since they are already implicitly specified when one has
specified all the B-facts.") Let us now return to the historical path
of the concept.
As Kim and others have pointed out, it seems that both some version of
the concept and the term 'supervenience' were in operation before
Moore's and Hare's usage in the context of the British Emergentist
School. The emergentist's understanding of supervenience, being more
in line with the vernacular sense, does not match the current
understanding as well as Moore's and Hare's. See McLaughlin 1992 for
an excellent analysis. Indeed, supervenience, as a concept, most
likely has much earlier roots than this, and one can readily find
examples (or approximations, at least) littered throughout the history
of philosophy. Leibniz's theory of space and time might be one such
example, with spatial and temporal properties supervenient on
non-spatial and non-temporal events. Hume's theory of causation might
be another example, with cause and effect supervening on sequences of
events that do not have causal properties. However, for the purposes
of a cleaner exposition we will stick with the orthodox historical
trajectory of supervenience. Not many philosophers initially picked up
on Hare's use of supervenience, but new life was breathed into it when
Donald Davidson (1970) utilized it to provide some of the support for
his anomalous monism. For example, in an oft-quoted passage he writes:
Although the position I describe denies there are psychophysical
laws, it is consistent with the view that mental characteristics are
in some sense dependent, or supervenient, on physical characteristics.
Such supervenience might be taken to mean that there cannot be two
events alike in all physical respects but differing in some mental
respect, or that an object cannot alter in some mental respect without
altering in some physical respect.
(Davidson 1970, p.214)
Davidson uses this supervenience relation to defend a non-reductive,
but nonetheless non-dualist, position with regard to the way in which
the mental stands to the physical (that is, psychophysical
supervenience). Though the mental is certainly dependent upon the
physical, in the sense that the physical determines the mental, it
cannot be reduced to it since there are no psychophysical laws while
there are, of course, physical laws:
[P]sychological characteristics cannot be reduced to the others,
nevertheless they may be (and I think are) strongly dependent on them.
Indeed, there is a sense in which the physical characteristics of an
event (or object or state) determine the psychological
characteristics…
(Davidson 1973, p. 716)
Once it entered the mainstream literature via Davidson, other
philosophers (Jaegwon Kim in particular) began to focus on
supervenience as an object of study in its own right—the 1984 Spindel
conference saw the beginnings of much of this new direction (see
Horgan (ed.), 1984—required reading for those wishing to gain a deeper
appreciation of the foundations of supervenience). This trend shows no
signs of letting up, though there is certainly some increased
negativity about the concept's usefulness and significance. A large
part of the perceived problem with supervenience is that there is no
unique, agreed-upon formulation of it. Instead there are many distinct
formulations. However, this might not be such a bad thing; different
jobs may require different tools. It is entirely possible that the
fortunes of supervenience will reverse with the coming of age of the
so-called "science of complexity," for this involves direct
consideration of the relationship between levels in hierarchies
whereby a higher level is generated by the level below—it also
involves many of the "special sciences." Supervenience might thus
provide the required conceptual framework to make sense of this
feature of complex systems. It has, for example, been endorsed by
Elliot Sober (1993) as the best way of understanding the biological
concept of "fitness," the idea being that fitness is something
exhibited by very different species and individuals in relation to
very different environments.
3. The Unlovely Proliferation of Formulations
We come now to the "embarrassment of riches" issue concerning the
formulation of supervenience—the problem of there appearing to be too
many possible formulations. David Lewis refers to this as an "unlovely
proliferation" (1986, p.14). The proliferation arises simply in trying
to pin down what is meant by supervenience in a precise way. The core
idea that a formulation needs to capture is that fixing some one set
of properties fixes some other property (or properties). The first
distinction we meet is that between weak and strong supervenience.
These can be stated simply enough in plain English as follows:
[Weak-SV]: For any possible world w, B-duplicates in w are A-duplicates in w.
[Strong-SV]: For any possible worlds w and w*, B-duplicates (x and y)
in w and w* respectively are A-duplicates in w and w* respectively.
So, for example, according to Weak-SV, if we (perhaps here on our
'plain vanilla' Earth) managed to create a Star-Trek style replication
machine and proceeded to replicate the physical makeup of a person P,
generating a copy Prep, then P and Prep would share their mental
characteristics too: "same worldly" physical duplicates are also
mental duplicates. To understand Strong-SV we simply imagine that some
Twin-Earthlings (in another possible world) got hold of an exact
blueprint of P and are sufficiently advanced to be able to create a
physical replica. Once again P and Prep are mental duplicates since
they are physical duplicates. (By simply setting w = w*, and assuming
the same types of worlds, we see that Strong-SV implies Weak-SV, but
not vice versa.)
The difference between Weak and Strong supervenience, then, simply
boils down to their respective modal strengths. One world is
quantified over in the former, with objects compared within a world,
while all worlds (subject to some restriction) are quantified over in
the latter, with objects compared across worlds. For this reason
Jackson (1998, p. 9) refers to these types as "intra-world" and
"inter-world" supervenience respectively. Clearly the weak formulation
cannot support basic counterfactuals of the form "if there were some
B-duplicate of some object, then it would be an A-duplicate too."
Without this ability, Weak-SV is pretty much useless, for some
dependency might be purely accidental. For example, it is perfectly
consistent with Weak-SV that there be a world physically identical to
ours yet with no conscious beings. (Though, of course, if one wants to
describe such possibly accidental relations then Weak-SV might indeed
be the right tool for the job.) Note also that Weak-SV does not tell
us that a certain group of B-properties makes one morally good, or a
piece beautiful, or a piece of matter alive. All Weak-SV tells us is
that B-twins are A-twins; it does not tell us whether B-twins are one
way or the other morally speaking, for example, just that whatever
goes for on goes for the other. Hence, it fails to accomplish the task
we set it: namely, to encode a notion of dependence and determination.
Strong-SV gets around this problem of course, but it has its own
problems. Suppose that there are two individuals, Fred and Ted,
inhabiting worlds w and w* respectively. Let Fred and Ted be "almost"
B-duplicates, differing only in one single trivial B-property, suppose
one is wearing aftershave and the other is not. Then it follows from
Strong-SV that Fred could be conscious but Ted not, all because he
didn't remember to put aftershave on!
There are alternative "modal operator" [MO] versions of the weak and
strong formulations of supervenience. Again in "plain" English, these
are:
[MO-Weak-SV]: Necessarily, if anything has property F in A, then there
is some property G in B such that the thing has G, and whatever has G
has F.
[MO-Strong-SV]: Necessarily, if anything has property F in A, then
there is some property G in B such that the thing has G, and
necessarily whatever has G has F.
The only difference between strong and weak here is that the strong
formulation features an additional necessity operator. What these
definitions amount to is this: Weak supervenience holds at any world
(given restrictions on the class of worlds), and once that world is
selected one compares B-duplicates, in that world, and sees whether
they are A-duplicates, if weak supervenience is true then they will
be. Strong supervenience holds at any world (again, given restrictions
on the allowable worlds), and once a world is selected it follows that
at any world accessible from that world, objects in the initially
selected and the accessed world that are B-duplicates, will be
A-duplicates—hence, one can compare cross-world cases. The modal
operator versions capture something that the possible worlds
formulations miss, namely that possession of a supervenient property
demands that a subvenient one be had as well. So, in the possible
worlds formulation, two things can be B-duplicates by not possessing
any B-properties (that is, if they exactly zero B-properties)! Not so
in the modal operator versions.
Another distinction concerns that between Weak-SV and Strong-SV, taken
as a pair, and Global supervenience, which we can write as:
[Global-SV]: Possible worlds w and w* that are B-duplicates are also
A-duplicates.
Thus, whereas Weak-SV and Strong-SV concern the properties of
individual objects (within a world and potentially across worlds
respectively), Global-SV concerns whole possible worlds and the
pattern of properties distributed over them. One might wish for such a
formulation to capture certain philosophical theses, such as
physicalism (roughly: fixing the physical facts fixes everything),
Humean supervenience (roughly: everything is fixed by the
spatiotemporal distribution of local intrinsic properties), or
determinism (roughly: everything to the future is fixed by the
present, and perhaps past, facts), which involve worlds (or 'world
segments') taken as individual objects. In each formulation, though,
we can distinguish between cases with differing modal force by
quantifying over different types of possible world (that is, by
imposing different accessibility relations on the set of worlds). An
accessibility relation is just a binary relation RMod (w, w*) holding
between pairs of worlds, w and w*, so that RMod (w, w*) is true
whenever w* satisfies the same M-laws (of physics, logic, and so
forth) as w. If you're only bothered about relations satisfying our
laws of physics, then you will only want to consider the nomologically
possible worlds, in which case RNom (w, w*) whenever w* follows the
same physical laws as w. If you want to go beyond our laws, then
quantification over the metaphysically possible worlds is more
appropriate (one needs to 'expand' the accessibility relation).
There is some confusion in spelling out what is meant in saying that
worlds are B-duplicates. Does it mean that the worlds may differ in
other ways, so long as they do not differ with respect to
B-properties? For example, might we consider two worlds B-duplicates
where one world, but not the other, has ghosts (with C-properties)? If
they are B-duplicates, and B-properties account for all there is, and
the worlds contain the same individuals, then what distinguishes such
worlds? These issues can cause problems when one tries to put
supervenience to work. Moreover, Global-SV faces a similar problem to
that mentioned with regard to Strong-SV. So long as two worlds are not
B-duplicates they can differ in any way you like with respect to their
A-properties. For example, if one single atom is out of place, then
this could mean that one world has conscious beings and the other
world only has zombies!
A further distinction is to be made between "single domain
supervenience" and "multiple domain supervenience." The difference
here concerns whether we wish to consider the A- and B-properties
associated to the same or to different things respectively. In the
latter, multiple domain case, one would look at those cases where
there cannot be A-differences in one thing without a B-difference in
some other distinct thing. Thus, weak and strong are clearly single
domain formulations. The multiple domain account has several
applications: for example, in the case of the problem of material
composition (for example, the way a statue stands to the lump of clay
that out of which it is composed), those who believe that the statue
and the clay literally coincide (share their spatial boundaries at a
time, if not for all time, and indeed these divergent histories is
what makes them different—they can also differ in their modal
properties, so that they satisfy different counterfactuals) will want
to say that the statue supervenes on the clay. But since these are two
different things, according to the coincidence advocate, w will need a
multiple domain account. For the same reasons, those who view
societies, or other similar structures, as separate objects,
autonomous from the individuals from which they are composed, will
need a multiple domain account if they wish to say that social
properties supervene on the properties of the underlying individuals.
(One can also formulate "local" or "regional" supervenience, which
restrict the supervenience relation to a spacetime region within a
world, rather than some concrete object within a world. Again, this
splits into weak and strong versions.)
There is something of a cottage industry devoted to spelling out the
various entailment relations between the various formulations. We saw
that Strong-SV implies Weak-SV, and it looks like Strong-SV implies
Global-SV too. However, the converse is trickier: given a certain
understanding of the properties involved, they become equivalent.
However, equivalence is ruled out by a simple counterexample (due to
Petrie): Suppose we have two worlds w and w*, each with two properties
A = {S}| and B= {P}, and two individuals x and y (and no more) in
world w, and x* and y* (and no more) in world w*. The world w is
characterized by the following distribution of properties over its
individuals: Px, Sx, Py, ~Sy. While world w* is characterized by the
distribution: Px*, ~Sx*, ~Py*, and ~Sy*. Clearly, strong supervenience
is ruled out by this model since x and x* are B-duplicates but not
A-duplicates. But this isn't incompatible with global supervenience
because the worlds are not B-duplicates, so A-duplication is
irrelevant. The fact that this model is consistent with global
supervenience yet inconsistent with strong supervenience is enough,
says Petrie, to show that they are not equivalent. There are
objections to this argument, but we shan't go in to these matters
here. Let us instead turn to some controversial issues that arise in
contemporary debates.
4. Supervenience and Causation
Supervenient properties are often those to which we wish to attach
causal powers. For example, mental effects from mental causes and even
physical effects from mental causes. If one thinks of an old love it
may cause one to feel sad, or have some other emotion. It may cause
one to cry. But the mental supervenes on the physical, which means
that the physical fixes the mental. So both mental causes and mental
effects are supervenient on some physical conditions. But then the
mental cause is irrelevant here since the physical conditions are
sufficient to bring about the effect. At best, the mental effect is
over-determined by the mental and physical causes. At worst, it leads
to epiphenomenalism about mental properties. Presumably the ground of
the supervenience relation will be relevant here.
If the supervenient properties are understood as emergent, then it is
possible that some "global" properties, to do with a whole system, can
causally effect other things, and its parts (the supervenience base).
For example, a group of agents can interact to generate an economy,
but the economy has properties of its own (prices, interest rates, and
such like); these will be able to influence how the agents behave. In
other words, there is the possibility of a 'feedback loop' from global
to local. Such a possibility would appear not to be available in the
case of a "mereological" grounding of a supervenience relation,
according to which the whole is just identified with the sum of its
parts. In the former case, the whole is supposed to be some how more
than the sum of its parts (due to the non-linear nature of the
interactions between the parts). But, nonetheless, in both cases, once
we fix the subvenient properties, we fix the supervenient ones too.
However, there are very problematic causal issues involved in the case
with a feedback loop where we would appear to have "downward
causation" so that the supervenient properties constrain and even
modify the subvenient ones. The existence of a "preferred direction"
to the relation seems to have been lost in such cases. This is an
interesting topic in need of much further work, but we cannot pursue
it further here.
5. Reduction, Emergence, and Multiple Realization
Reductionism is as old as philosophy itself. The ancient Greek
cosmologists each defended what appear to be reductive theories
according to which everything that exists is made up of some single
fundamental element or a group of such elements. Most apt here is the
version of atomism given to us by Leuccipus and Democritus according
to which all things, including secondary qualities, souls, and
thoughts, were reduced to atoms moving in the void. But there are some
things that, it seems, are not easily reducible. Take Beethoven's
Fifth Symphony. How does one reduce this? To a sound structure (that
is, a sequence of sounds)? If so, then many different sound structures
can realize it, on CDs, Vinyl, a badly tuned piano, and so on. This
piece of music is, then, multiply realizable (there is a many-to-one
relationship between the subvenient realizations and the supervenient
property). We might also consider some "higher order" properties of
musical works, say "being a grand piece of music." This property too
is multiply realizable: there are many ways to be a grand piece of
music. This seems to rule out reduction, at least to a unique sound
structure. But, and here we return to Hare's example, if there are two
indistinguishable realizations, then if one is a grand work of music,
the other cannot fail to be. The grandeur is determined by the sound
structure—we are, of course, assuming that grandeur is a property
intrinsic to a work, otherwise one and the same sound structure could
be both grand and not grand.
This multiple realizability lies at the core of supervenience's job,
namely, to describe a dependency weaker than identity and reduction.
The idea is, that fixing the physical properties of the work of music
(the tones, durations, intensities, and so on) suffices to fix any and
all aesthetic properties the piece might have. But then the idea of
emergence amounts to the claim that these aesthetic properties (and
similar higher-level properties) are not reducible to the physical
ones, they are something "novel" arising from the physical
organization. (The distinction between physical and non-physical
properties here amounts to both the fact that the latter type can be
had by many objects with different natures and constitutions, and the
fact that the former type obey the laws of, possibly complete,
physics. However, nothing said here hinges on this distinction, one
might as well say that aesthetic properties are physical too, since
they occupy the world. Thus, this is just a way of speaking to label a
curious fact, namely that some properties seem not to be reducible to
what are standardly taken to be unproblematic 'physical' properties,
such as mass, charge, spin, and so on.) Dualism and epiphenomenalism
are avoided (1) because the physical facts are needed to fix the
emergent facts and (2) because the emergent properties are supposed to
be causally efficacious: the beauty of the Adagio from Mahler's Fifth
Symphony can cause a person to cry; it isn't the durations,
intensities, and pitch of sounds that is causally responsible—though
one might conceivably take a hard line here and argue that it is
precisely the physical (subvenient) properties that cause the tears.
(Though it must be understood that causation is far from simple in
these contexts, as we saw in the previous section.)
In an early and pioneering work on supervenience and determination, in
the context of a defense and formulation of physicalism, Hellman and
Thompson were concerned with separating out supervenience from
reduction. Physicalism can be understood simply as follows: When God
made the World, did he just have to fix the facts regarding the
elementary particles and the forces (the B-properties) and all the
rest (the A-properties: colors, qualia, aesthetic properties, moral
properties, and so forth) followed from that, or did he have to then
attach all the rest? A physicalist will answer Yes to the former
question. Supervenience, or rather determination, is supposed to
support the affirmative answer, for it says precisely that the
B-properties determine the A-properties. Hellman and Thompson wanted
to show that supervenience is neutral in respect of reduction between
supervenient and subvenient levels of properties.
Why might we wish to defend the view that supervenience is
non-reductive? One reason, as we have seen, is to capture a notion of
ontological dependence—say of the mind on physical brain states or
processes—without eliminating the mind, or identifying the mind with
the brain states. The problem with such a view is that prima facie it
appears to let in 'unphysical' properties, that either amount to
dualism or epiphenomenalism. There is certainly a problem in making
ontological sense of supervenient properties, but one needn't espouse
either dualism or epiphenomenalism if one is committed to a
supervenience thesis. For all that is being said is that fixing some
one set of facts fixes some others. However, there is an argument that
attempts to demonstrate that supervenience is reductive. Let us
consider this argument, and then present one against reduction.
The argument is given in Kim's "Supervenience and Nomological
Incommensurables". In capsule form, it goes as follows: Suppose we
have two sets of properties, P (for physical) and S (for special, as
in special science). Let s be a property in S and let pn be the list
of properties contained in P. Define qn to be the set of maximally
conjunctive properties that can be built from pn (where the maximally
conjunctive condition means that for each pi, either pi or its
negation is a conjunct of qn). If S is supervenient on P then any pair
of objects that share some qi must both possess s or both lack s. Now,
let D be the disjunction of all of those qi such that if an object has
qi then it has s too. However, this implies that possession of an S
property is equivalent to possession of a P property. In other words,
for all x's, s has x if and only if D has x (in shorthand: x , s(x)
iff D(x)). This, of course, is tantamount to a reduction of S to P,
for the claim is that every higher level, supervenient, property is
coextensive with some Boolean complex of lower level, subvenient,
properties, say a long (possibly infinite) disjunction of properties.
Thus, any two objects with the supervenient property A must possess
the very same subvenient property B, but B is a very complex property
that will involve an exhaustive list of the ways that A could be had
by any object.
Hellmann and Thompson's strategy is to disallow infinite conjunctions
and disjunctions of properties, thereby blocking the route to the
infinitely complex properties that Kim's argument let in, and
therefore blocking the route to reduction. However, while an outright
ban on such properties may be otherwise well motivated, it is too ad
hoc in this case. A more promising approach to stop Kim's argument is
to simply not allow that the kind of Boolean operations that Kim
utilizes to generate new properties result in genuine properties. One
might apply this strategy either to negations of properties,
disjunctive properties, conjunctive properties, or some combination of
these (see McLaughlin's article "Varieties of Supervenience").
In his "Reduction of Mind" Lewis speaks of supervenience as a
reductive principle, going somewhat against the philosophical grain.
As a build up he writes:
I hold, as an a priori principle, that every contingent truth must
be made true, somehow, by the pattern of coinstantiation of
fundamental properties and relations [that is, occurring all
together]. The whole truth about the world, including the mental part
of the world, supervenes on this pattern. If two possible worlds were
exactly isomorphic in their patterns of coinstantiation of fundamental
properties and relations, they would thereby be exactly alike
simpliciter.
(Lewis 1994, p.292)
Lewis adds to this that all the fundamental properties and relations
are physical, so that a materialist thesis is generated from the
supervenience—the position amounts, more or less, to a statement of
his "Humean Supervenience;" the claim that "All there is to the world
is a vast mosaic of local matters of fact…And that is all" (1986,
p.ix-x) so that "truth supervenes on being" (1994b, p.225). But how
can supervenience be reductive? Lewis gives the following example:
Imagine a grid of a million tiny spots – pixels – each of which
can be made light or dark. When some are light and some are dark, they
form a picture, replete with interesting gestalt properties. The case
evokes reductionist comments. Yes, the picture really does exist. Yes,
it really does have those gestalt properties. However, the picture and
the properties reduce to the arrangement of light and dark pixels.
They are nothing over and above the pixels. They make nothing true
that is not made true already by the pixels. They could go unmentioned
in an inventory of what there is without thereby rendering that
inventory incomplete. And so on.
(Lewis 1994, p. 294)
Such comments Lewis happily endorses: "The picture reduces to the
pixels. And that is because the picture supervenes on the pixels"
(loc. cit.). Lewis' position here stems from the fact that the
supervenience relation is (in this case, at least) non-symmetric and
relates large to small—though it isn't at all obvious that this is
sufficient for reduction.
However, there is a way for the anti-reductionist to respond here, and
this response ties in to much of the contemporary debate regarding
supervenience (and emergence). The response is known as the "multiple
realizability" objection, and was first used by Jerry Fodor (1974) in
the context of the debate concerning the non-reducibility of special
science to lower-level science (ultimately, physics). The argument, in
a nutshell, is that properties associated to a 'special science' (for
example, psychology) can be realized by a multitude of heterogeneous
lower-level properties or states. Let us see how this works by
focusing on a simplified example given by Putnam (1975).
We are asked to consider a board that has a round hole in it of 5
inches in diameter, and a square peg that is 5 inches on each of its
sides. Clearly the peg will not go into the hole. The question we are
faced with is why the peg does not go through. Obviously, says Putnam,
the respective size and shape of the peg and hole give us the answer.
These properties, size and shape, Putnam refers to as
"macroproperties", as contrasted with the "microproperties," of the
peg and board, namely the positions, momenta, charge, and so forth, of
the atoms composing them. Clearly the shape and size of the peg and
the board supervene on the microproperties. Do these microproperties
provide an answer to the above question? Putnam says not, because the
details at that level are irrelevant to why the peg did not penetrate
the board: the microproperties could have been very different, in
fact, and the result would have been the same. What are we to conclude
from this? That the "peg/board/hole"-level features (the
macroproperties) are autonomous, so that they cannot be reduced to
lower-level features (the microproperties). This is, more or less,
just multiple realizability again, but here it keys in to an
interesting aspect of that concept. It tells us that what is
explainable using supervenient features is not always explainable
using the associated subvenient features. Here one can make
connections traditional issues with philosophy of science.
There are dissenting voices to Putnam's thesis, but we shall not go
any further into the ins and outs of the debate here since it quickly
becomes dense and complex. Suffice it to say that supervenience is
still "live" in many philosophical debates and will no doubt continue
to remain so for some time to come.
6. Adding Mystery to Mystery?
Supervenience is something of a halfway house. It is called upon by
some to ground a view according to which certain properties that we
think of as "unphysical" are not definable in terms of, or reducible
to physical properties and yet are nonetheless connected in some way.
It is supposed to somehow avoid the mystery of how physical matters
can have a determinative role to play in unphysical properties,
without those unphysical properties causing a problem in being
materialistically un-kosher. For others, supervenience is a reductive
principle, a matter of how the world is and must be.
Many philosophers have complained about the (in)significance of
supervenience. Stephen Schiffer suggests that the invocation of
supervenience simply moves the explanatory task back a step. How, he
asks,
could being told that non-natural moral properties stood in the
supervenience relation to physical properties make them any more
palatable? On the contrary, invoking a special primitive metaphysical
relation of supervenience to explain how non-natural moral properties
were related to physical properties was just to add mystery to
mystery, to cover one obscurantist move with another.
(Schiffer 1987, p.153-4)
Much recent work has been devoted to decrying the philosophical
utility of specific formulations of supervenience, the general idea,
or proving equivalences between them. All of the formulations we have
seen do no more than to chart certain correlations between properties.
They do not tell us anything about dependency or determination between
the properties, in the sense of, say, a causal relation. Supervenience
directs us to search for the underlying reasons for the correlation—it
might not always be there. In the case of the special sciences it
isn't clear that an "underlying reason" is to be found. Kim (1987, p.
167), for example, believes that supervenience is not a "deep"
metaphysical relation, but instead is a superficial relation that
points to some other 'deeper' relation that might explain the
superficial pattern of dependency—though more recently Kim has shifted
to a reductive view of the relation (see Kim, 2005, for a clear
account). In this sense, supervenience is a useful concept, for it can
function as a filter on types of relations, letting through those of a
certain type. Once we have identified a dependence relation, we can
then delve deeper to see what might account for it: causation,
mereology, definition, emergence, and so forth. In this sense there is
no question of supervenience being an explanatory device, so there is
no mystery here; but it can nonetheless be used in the search for
explanations.
Supervenience has many useful applications too, in making other areas
of philosophy clearer and more navigable. For example, the
internalism/externalism distinction concerning mental content [very
roughly, externalism is the view that mental content depends on things
outside of the mind as well as inside; internalism denies this—saying
that only what's inside matters] can be cast into the endorsement and
denial respectively of the following supervenience thesis: the content
of a mental state (that is, what it is about) supervenes on certain
neurobiological properties (narrow content). On the other hand, the
externalist, as can be discerned from the rough characterization
above, believes that there is more to content than this: the world
plays a role too. One can clarify the distinction between internal and
external relations too: an internal relation is one that supervenes on
the intrinsic properties of its relata (for example, being heavier
than), while this is not true in the case of external relations (for
example, being 2 miles away from); it does not matter what something
is like for it satisfy this latter relation, but it does for the
former. We have seen too that it allows for a definition of
physicalism and helps with the puzzle of material coincidence. Surely,
if by a concept's work shall you know it, supervenience deserves the
central place that it has found in the philosophers' toolbox.
7. References and Further Reading
For a more technical and detailed presentation of the concept of
supervenience, see McLaughlin and Bennett's article in the Stanford
Encyclopedia of Philosophy.
* Beckermann, A., Flohr, H., & Kim, J., (eds.). Emergence or
Reduction? Essays on the Prospects of Nonreductive Physicalism.
Berlin: Walter de Gruyter, 1992.
* Davidson, D. 1970. "Mental Events." In D. Davidson (ed.), Essays
on Actions and Events, 1980: 207-225.
* Davidson, D. "The Material Mind." In P. Suppes (ed.), Logic,
Methodology and the Philosophy of Science. North-Holland. Reprinted in
Essays on Action and Events (Oxford University Press, 1980).
* Fodor, J. "Special Sciences, or the Disunity of Science as a
Working Hypothesis." Synthese, 1974, 28: 97-115.
* Hare, R.M. The Language of Morals. Oxford: Oxford University Press, 1952.
* Hellman, G. & Thompson, F. "Physicalism, Ontology,
Determination, and Reduction," The Journal of Philosophy, 1975, 72:
551-64.
* Horgan, T. "From Supervenience to Superdupervenience: Meeting
the Demands of a Material World." Mind, 1993, 102: 555-86.
* Horgan, T. (ed.) Southern Journal of Philosophy 22: The Spindel
Conference 1983 Supplement. Supervenience, 1984.
* Jackson, F. From Metaphysics to Ethics. Oxford: Oxford
University Press, 1998.
* Kim, J. Supervenience, or Something Near Enough. Princeton
University Press, 2005.
* Kim, J. Supervenience and Mind. Cambridge University Press, 1993.
* Kim, J. "Concepts of Supervenience." Philosophy and
Phenomenological Research 1984, 45, 2: 153-176.
* Kim, J. "Supervenience as a Philosophical Concept." Reprinted in
J. Kim, Supervenience and Mind, 1993 (1990): 131-160.
* Kim, J. "'Strong' and 'Global' Supervenience Revisited."
Philosophy and Phenomenological Research, 1987, 48, 2: 315-326.
* Lewis, D.K. The Plurality of Worlds. Oxford: Oxford University
Press, 1986.
* Lewis, D. K. "Reduction of Mind." In D. Lewis (ed.), Papers in
Metaphysics and Epistemology. Cambridge University Press, 1999 (1994):
291-324.
* McLaughlin, B. & Bennett, K. "Supervenience." The Stanford
Encyclopedia of Philosophy (Fall 2005 Edition), edited by Edward N.
Zalta.
* McLaughlin, B.P. "The Rise and Fall of British Emergentism." In
A. Beckermann et al. (eds.), Emergence or Reduction? Essays on the
Prospects of Nonreductive Physicalism. Walter de Gruyter, 1992: 49-93.
* McLaughlin, B.P. "Varieties of Supervenience." In E. Savellos &
U. Yalcin (eds.), Supervenience: New Essays. Cambridge University
Press, 1995: 16-59.
* Moore, G.E. Philosophical Studies. London: Routledge, 1922.
* Paull, C.P. & Sider, T.R. 1992. "In Defense of Global
Supervenience," Philosophy and Phenomenological Research, 32, 1992:
830-45.
* Post, J. F. "Comment on Teller." In Horgan (ed.), The Spindel
Conference 1983 Supplement. Supervenience, 1984: 163-167.
* Putnam, H. "Philosophy and our Mental Life." In Mind, Language,
and Reality. Cambridge University Press, 1975.
* E. Savellos & U. Yalcin (eds.), Supervenience: New Essays.
Cambridge University Press, 1995.
* Schiffer, S. Remnants of Meaning. Cambridge, Mass.: MIT Press, 1987.
* Sober, E. The Nature of Selection: Evolutionary Theory in
Philosophical Focus. University of Chicago Press, 1993.
* Stalnaker, R. "Varieties of Supervenience." Philosophical
Perspectives 10, 1996: 221-241.
* Teller, P. "A Poor Man's Guide to Supervenience and
Determination." In Horgan (ed.), The Spindel Conference 1983
Supplement. Supervenience, 1984: 137-50.
No comments:
Post a Comment