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Copyright © Interdisciplinary Encyclopedia of Religion and Science ISSN: 2037-2329 and John Polkinghorne
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To refer to the content of this article, quote: INTERS – Interdisciplinary Encyclopedia of Religion and Science, edited by G. Tanzella-Nitti, P. Larrey and A. Strumia, http://www.inters.org
 Reductionism
John C. Polkinghorne
I.
Types of reductionism - II. Hierarchy and emergence - III. Insights
from science - IV. Philosophical and theological aspects of reductionism.
1. Rationality. 2. Metaphysics. 3. Theological
issues. - V. Concluding remarks. 1. Levels of description.
2. One world.
A reductionist believes that a complex system is nothing but the
sum of its parts. An account of it can be reduced to accounts of
individual constituents. An antireductionist believes that the whole
is more than the sum of its parts. There are holistic properties
that cannot be described in purely constituent terms.
I. Types of Reductionism
Constituent reductionism accepts that when a complex system
is actually decomposed, the resulting fragments will just be those
corresponding to the expected constituents. For example, a living
organism can be split up into its component molecules and there
will not be any extra ingredient left over, such as the spark of
life that vitalism claimed distinguished living entities from inanimate
matter. This type of reductionism is very widely accepted. It by
no means implies, however, that living beings are “nothing
but” collections of molecules, for the decomposition will have
brought about the death of the organism. Reductionism of this kind
is closely related to methodological reductionism, the widely
practised scientific strategy of studying wholes through breaking
them up into their constituent parts. Again, the success of the
strategy does not imply that everything relevant to the whole can
be studied in this way.
A second type of reductionism may be called conceptual reductionism, in which it
is claimed that the concepts applicable to the whole can be totally expressed in terms of
concepts applying to the parts. The term epistemological reductionism is also used
for this type. An example of a successful reduction of this kind is afforded by the use of
the kinetic theory of gases to reduce the concept of temperature (originating in the
thermodynamics of bulk matter) to exact equivalence to the average kinetic energy of the
molecules of the gas. However, there are many examples that suggest that reductions of
this kind cannot always be made. Individual water molecules do not possess the property of
wetness, which is a conceptually irreducible aspect of the behaviour of large collections
of such molecules (generated by the inter-molecular forces that are the source of the bulk
property called surface tension). Biological science makes use of many essential concepts,
such as fitness, adaptation, organ, sexuality, ecological niche, which cannot be
translated into statements about molecules.
A third type is causal reductionism, which implies that
the causes acting on the whole are simply the sum of the effects
of the individual causalities of the parts. In the case of wetness
such a reduction appears successful, on the reasonable supposition
that surface tension is generated entirely by the action of inter-molecular
forces. Since at both levels one is concerned with purely energetic
properties, a translation between the two seems plausible. On the
other hand, it is not at all clear that sums of firings of neural
synapses can add up to produce mental qualia (feels),
as there appears to be a clear qualitative difference between the
two ( MIND-BODY
RELATIONSHIP). Causal reductionism is closely allied to ontological
reductionism, the assertion that the whole is the sum of its
parts. It is quite possible to hold to constituent reductionism
and to deny causal reductionism as, in fact, many do. One strategy
for this is to embrace contextualism, the belief that the
behaviour of constituents depends upon the nature of the whole that
they constitute.
II. Hierarchy and Emergence
If all three types of reduction hold, a position one might call
strong reductionism, then the truly basic ontology is exclusively
that of the fundamental constituents. All the rest is mere elaboration.
From such a point of view, elementary particle physics is the foundational
discipline, and everything else, including the rest of physics,
through biology and on to psychology, anthropology and sociology,
would be just a collection of corollaries. This would constitute
the modern equivalent of the ancient assertion that all is “atoms
and the void” (
MATERIALISM, I). Of course, such a claim could only be made in principle,
as the drawing of these corollaries would be very far beyond human
capacity. Even in physics, the totally adequate description of a
macroscopic lump of matter would involve discussing the behaviour
of a collection of atoms of the order of 1023 in number. In other
words, reductionist or antireductionist claims are always metaphysical
in character. They may be motivated by extrapolations from results
in the natural and the human sciences, but they can never be fully
substantiated by scientific arguments alone.
In practical terms, therefore, there is a hierarchy of the sciences, in which the
“higher”draws upon the resources of the “lower”, but
it needs also to make use of its own style of argument and conceptual apparatus in
addressing the problems posed by its own particular phenomena. Chemistry is related
to physics in this way, and biology is similarly related to both of them.
Above biology, lies the succession of the human sciences: psychology, anthropology,
sociology. The hierarchy is ordered in a natural way that depends upon some concept of
increasing complexity. Although there are technical difficulties in the precise definition
of the meaning of increase in complexity, it is intuitively persuasive that the sequence:
quark, molecule, cell, multicellular entity, conscious being, self-conscious being,
represents an ascending scale of this kind. It is important to recognise that it is not
merely size that is the essence of complexity, but the degree of intrinsic
inter-relationship and mutuality present between the parts. Although the observable
universe contains 1022 stars, cosmology is a great deal simpler subject than human
biology.
The levels of a hierarchy can be distinguished by the emergence at a higher
level of properties that are not manifested at lower levels. Life and
consciousness are the two most striking instances of emergence that are known to us. A
critical question is whether the phenomenon of emergence is simply the expression of
conceptual antireductionism, or whether it is of deeper ontological significance. We have
seen that the emergence of the wetness of water seems to be simply an example of the
conceptual kind, in which energetic properties at one level produce energetic properties
at the higher level in an unproblematic way. On the other hand, the emergence of
consciousness appears to be one that resists understanding in purely conceptually emergent
terms. A big gap yawns between methodologically reductive accounts of neural processes and
the simplest conscious mental experiences, such as feeling hungry or seeing blue, with no
obvious bridge between the two. This recognition raises the question of whether there may
not also be causal antireductionism involved in this case. If the execution of mental
intentions is a free act of the human person, this would then seem to the case, for an
irreducibly holistic causality (human intention) would be acting.
Finally, we may note that people of a strongly reductionist tendency,
such as Francis Crick (1994) and Richard Dawkins (1976), do not
go below the level of their own discipline for explanatory purposes,
but are content to frame their accounts in terms of molecules or
genes, without pressing on to the quark level.
III. Insights from Science
It is useful to note a number of indications from modern science
that encourage adopting an antireductionist stance:
a) Contrary to the Newtonian picture of a physics concerned with atoms
moving in the void of a spatial container ( MECHANICS,
III.1), Einstein`s general relativity
ties together space, time and matter in intrinsic inter-relationship.
b) The EPR effect [Einstein, Podolski, Rosen] shows that once two quantum
entities have interacted with each other, they remain mutually entangled,
however far they separate, so that effectively they remain a single
system ( QUANTUM
MECHANICS, V). The subatomic world cannot properly be described
in atomistic terms.
c) Complex physical systems display many properties that could not have been foreseen
from consideration of their constituents on their own. For example, electrons moving in
metals have a band structure for their energy levels. This means that there are some
ranges of energy that are accessible to them and some which are not. This is in complete
contrast to the behaviour of individual free electrons, whose energies can take any value.
d) Chaos theory (cf. Gleick 1988) is the study of systems that are exquisitely
sensitive to the finest detail of their circumstances, so that the slightest change in
their surroundings totally changes their future behaviour. Such systems are widespread and
their environmental vulnerability means that they are not truly isolatable. They must,
therefore, be considered holistically, in their total context.
e) Complexity theory (cf. Kauffman 1995) is concerned with the behaviour of complex
systems (see above, c) whose constituents are inter-related in some specific way. At
present in its infancy and largely based on computer modelling, this new science has shown
that systems of this kind are capable of spontaneously generating astonishing degrees of
overall pattern in their behaviour. This has suggested to some that when a proper
formulation of the theory is found, it will involve not only exchanges between
constituents but also a kind of holistic pattern-forming capability which has been dubbed
“active information” (cf. Polkinghorne 1998a).
f) Biological cells are biochemical systems of great inter-related
complexity. Although it has become conventional to talk of DNA as
carrying information (
BIOLOGY, IV), this informational content is only meaningful and
activated within the total context of the living cell. In isolation,
DNA is no more than a very complex chemical.
g) The Nobel prize-winning brain scientist, Roger Sperry (cf. Sperry,
1983), introduced the concept of “top-down causality”,
the influence of the whole upon its parts which he believed was
involved in the causal transactions taking place between mind and
brain. The idea of top-down causation has subsequently been taken
up by a number of other writers.
IV. Philosophical and theological aspects of reductionism
1. Rationality. Strong reductionism faces a problem in relation
to the nature of rationality. If reality is no more than the interactions
of elementary particles, then everything just happens and who is
to say that the mouthings of human automata are the articulations
of rational discourse? What could authenticate that utterance as
being valid and truthful? The strong reductionist saws off the very
branch on which he seeks to sit, by putting in jeopardy the arguments
believed to defend his position.
2. Metaphysics. The classical philosophical positions of
physicalism or idealism are both essentially reductionist in character,
as they reduce reality simply to the material or to the mental.
Substance dualism, of a Platonic or Cartesian kind, is essentially
antireductionist in the sense of allowing reality both to the material
and to the mental. However, it has encountered many problems, rooted
in its difficulty in explaining how the mental and the material
relate to each other. There are a number of other contemporary philosophical
positions that are also antireductionist in character.
One is dual-aspect monism (sometimes also called non-reductive
physicalism) which asserts that there is only one kind of substance
but that it can be experienced the two complementary poles of the
material and the mental. Such an even-handed treatment of mind/matter
is antireductionist. In a different way, A.N.Whitehead`s
(1861-1947) process thought also resists reductionism. It is based
on a metaphysics of individual events (“actual occasions”).
These can be of varying degrees of complexity and they are not to
be reduced to a single common denominator. Another antireductionist
proposal was made by Niels Bohr (1885-1962) when he suggested exporting
from quantum mechanics his concept of complementarity and using
it as a way of relating life and matter. Bohr emphasised the point,
already noted, that reducing a living entity to its molecular parts
serves to kill it, so that encountering it in its holistic integrity
or in its material decomposition are mutually incompatible alternatives.
None of these metaphysical formulations, however, are without their
difficulties.
3. Theological Issues. It is scarcely necessary to emphasise
the interest of theology in an antireductionist understanding of
reality. From Lucretius (98-54 B.C.) onwards, those who have supposed
that there is nothing but atoms and the void have also espoused
atheism.
The reality of the mental and the spiritual is vital to religion,
and the reality of the material is vital to Christianity, the religion
of the Word made flesh ( JESUS
CHRIST, INCARNATION AND DOCTRINE OF LOGOS, IV). Theology should
take heart from the fact that there is sufficient encouragement,
both from science properly construed and from philosophy carefully
pursued, to defend the antireductionist position.
V. Concluding remarks
1. Levels of description. The knowledge we obtain from our
exploration of the world (we report here what already written elsewhere,
cf. Polkinghorne, 1987, pp. 86-87 and pp. 97-98), can be organized
into a hierarchy, corresponding to the complexity of the systems
treated as basic: physics, chemistry, biochemistry, biology, psychology,
sociology, theology. The question is how these different levels
of description relate to each other. The thorough-going reductionist
offers us an answer: ultimately all is physics ( POSITIVISM).
Everything else is nothing but an epiphenomenal ripple on the surface
of a physical substrate, just as waves generated by the wind in
a field of corn are nothing but the motions of many ears of wheat.
It is an answer of great simplicity and implausibility. I a Rembrandt
self-portrait nothing but a collection of specks of paint? A Shakespearean
sonnet nothing but a pattern of ink marks on a sheet paper? If we
take the picture or the printed poem apart that is all we shall
find. There will not be an extra ingredient, the spirit of art or
poetry, to be found in the residue. It seems to me that we can accept
a structural reductionism, that the units out of which all the entities
of the physical world are constructed are just the elementary particles
studied by fundamental physics. In biology vitalism seems justly
dead. The successes of molecular biology do not encourage us to
believe that a mysterious entelechy or élan vital is an additive
necessary to turn inanimate matter into living being. It is an entirely
different proposition to add to this , as our thorough-going reductionist
does, a conceptual reductionism which denies the emergence, with
increasing complexity of organization, of totally new levels of
meaning and possibility which are not in principle reducible to
those which lie below them. If structural reductionism is not to
lead to conceptual reductionism a careful investigation is necessary
into the extent to which genuine novelty can come into being with
these increasing degrees of organization. To what extent is the
whole more than the sum of its parts? It must surely be through
the enhancing effect of mutual co-operative interaction, made possible
by integrating components into a larger unity.
I believe that those who defend the autonomy of their subject against the
imperialist claims of physics are right to do so. Animals are made of atoms but that does
not imply that biology is just a complicate corollary to atomic physics.
Characteristically, biological concepts need for their understanding the total living
setting in which they find their expression. Consider a sentence like:
«molecular biology has given us considerable biochemical insight into how the
genetic blueprint is encoded onto DNA and how messenger RNA transfers appropriate parts of
that plan to control the production of proteins». It speaks a hopelessly mixed
language. Biochemistry can talk about the molecular dynamics of aggregating amino acids to
form proteins. The information-carrying language of “blueprint” and
“plan” refers to a different and disjoint type of discourse which only
begins to make sense in a cellular context.
2. One world. It was said, perhaps unjustly, of the great 19th
century experimental physicist Michael Faraday, who was a committed
Christian believer, that when he went into his laboratory he forgot
his religion and when he came out again he forgot his science. I
hope that it is not true. We live in one world and science and theology
explore different aspects of it. The burden of our tale has been
that, despite the obvious differences of subject matters, the two
disciplines have in common the fact that they both involve corrigible
attempts to understand experience.
They are both concerned with exploring , and submitting to, the
way things are. Because of this they are capable of interacting
with each other: theology explaining the source of the rational
order and structure which science both assumes and confirms in its
investigations of the world; science by its study of creation setting
conditions of consonance which must be satisfied by any account
of the Creator and his activity. The relationship is not free from
puzzles but I have sought to show that no act of mental compartmentalism
or dishonest adjustment is required of those who take with equal
seriousness the stories told by science and by faith.
Reality is a multi-layered unity. I can perceive another person as
an aggregation of atoms, an open biochemical system in interaction
with the environment, a specimen of homo sapiens, an object
of beauty, someone whose needs deserve my respect and compassion,
a brother for whom Christ died. All are true and all mysteriously
coinhere in that one person. To deny one of these levels is to diminish
both that person and myself, the perceiver; to do less than justice
to the richness of reality. part of the case for theism is that
in God the Creator, the ground of all that is, these different levels
find their lodging and their guarantee. He is the source of connection,
the one whose creative act holds in one the world-views of science,
aesthetics, ethics and religion, as expression of his reason, joy,
will and presence (
CREATION).
This interlocking character of the world of creation finds its fullest
expression in the concept of sacrament, an outward and visible sign
of an inward and spiritual grace ( SYMBOL,
IV), a wonderful fusion of the concerns of science and theology.
Thus in the Eucharistic bread and wine which, in the words of liturgy,
«earth has given and human hands have made», become
the body and the blood of Christ, the source of spiritual life.
The greatest sacrament, compared to which all the others are types
and shadows, is the Incarnation in which «the Word became
flesh and dwelt among us, full of grace and truth; we have beheld
his glory, glory as of the only Son from the Father» (Jn
1,14). The Word, the Lógos, combines two notions, one Greek,
one Hebrew. For the Greek the lógos was the rational ordering
principle of the universe. For the Hebrew the word of the Lord was
God’s activity in the world. Science discerns a world of rational
order developing through the unfolding of process, a fusion of Greek
and Hebrew insights. Theology declares that world in its scientific
character to be an expression of the Word of God. For «all
things were made through him, and without him was not anything made
that was made» (Jn 1,3).
John C. Polkinghorne
See also: ANALOGY;
BIOLOGY; COMPLEXITY; MATTER; MATERIALISM; POSITIVISM; PRAGMATISM.
Documents
of the Catholic Church related to the subject
Bibliography
R. DAWKINS, The Selfish Gene, Oxford
Univ. Press, Oxford 1976; R.W. SPERRY, Science and Moral Priority,
Columbia Univ. Press, New York 1983; A.R. PEACOCKE, God and the
New Biology, Dent, London 1986, chs. 1-4; J. POLKINGHORNE, One
World. The Interaction of Science and Theology, Princeton Univ.
Press, Princeton (NJ) 1987; J. GLEICK, Chaos, Heinneman,
London 1988; I.G. BARBOUR, Religion in an Age of Science,
Harper and Row, New York 1990, pp. 165-171; E. Agazzi (ed.), The
Problem of Reductionism in Science, Kluwer, Dordrecht 1991;
F.H.C. CRICK, The Astonishing Hypothesis, Simon and Schuster,
London 1994; S. KAUFFMAN, At Home in the Universe, Oxford
Univ. Press, New York 1995; J.C. POLKINGHORNE, Belief in God
in an Age of Science, Yale Univ. Press, New Haven 1998, ch.
3; J.C. POLKINGHORNE, Science and Theology, SPCK, London
1998, pp. 50-62.
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