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Pain as metaphor: metaphor and medicine
Shane Neilson
Correspondence to
Shane Neilson, Department of
English and Cultural Studies,
Chester New Hall 321,
McMaster University, 1280
Main Street West, Hamilton,
ON L8S 4L9, Canada;
neilss@mcmaster.ca
Accepted 17 July 2015
To cite: Neilson S. Med
Humanit Published Online
First: [please include Day
Month Year] doi:10.1136/
medhum-2015-010672
ABSTRACT
Like many other disciplines, medicine often resorts to
metaphor in order to explain complicated concepts that
are imperfectly understood. But what happens when
medicine’s metaphors close off thinking, restricting
interpretations and opinions to those of the negative
kind? This paper considers the deleterious effects of
destructive metaphors that cluster around pain. First, the
metaphoric basis of all knowledge is introduced. Next, a
particular subset of medical metaphors in the domain of
neurology (doors/keys/wires) are shown to encourage
mechanistic thinking. Because schematics are often used
in medical textbooks to simplify the complex, this paper
traces the visual metaphors implied in such schematics.
Mechanistic-metaphorical thinking results in the
accumulation of vast amounts of data through
experimentation, but this paper asks what the real value
of the information is since patients can generally only
expect modest benefits – or none at all – for relief from
chronic pain conditions. Elucidation of mechanism
through careful experimentation creates an illusion of
vast medical knowledge that, to a significant degree, is
metaphor-based. This paper argues that for pain
outcomes to change, our metaphors must change first.
For most patients, pain is transient, lasting as long
as the causal illness does. Then pain disappears. For
other patients, pain transforms into a chronic
problem that usurps identity. Both types of patients
want release, for their ordeal to end. But in the lan-
guage I just used, that of ‘patients’ and ‘illness’ and
‘problem’ and ‘ordeal,’ I have perpetuated a
‘problem’ that is consolidated in language. In her
landmark study The Body in Pain, Elaine Scarry
memorably pointed out that pain finds its way into
language almost exclusively through metaphors of
weaponry and damage.
1
I build on this observation
by arguing that pain is conceptualised and
expressed through negative and destructive meta-
phorical systems that have been appropriated by
physicians and entrenched with supplementary
neurological metaphors. I argue further that the
incredible accumulation of detail concerning pain
pathways is dependent upon these destructive meta-
phor systems. The medical understanding of pain is
reliant upon certain theoretical constructs that
might be distant in time yet are influential in effect;
elaborations upon these theories with experimental
knowledge and minute elaboration of physical
detail—the so-called ‘mechanistic’ view of pain—
do not change the metaphors we use to understand
the physiological information. Because the benefit
of seeing a medical practitioner skilled in the treat-
ment of pain is modest, the accumulation constitu-
tes a meaningless ubiquity, an authoritative edifice
of medical knowledge that is an illusion of author-
ity. That the authority derives from knowledge that
is based on destructive metaphors should make
anyone suffering from pain circumspect.
In Metaphors We Live By, a seminal text on meta-
phor, Lakoff and Johnson define metaphor as “a
way of conceiving of one thing in terms of another,
and its primary function is understanding”.
2
All
disciplines resort to metaphor for the means of
their understanding, and Lakoff and Johnson dem-
onstrate how pervasive metaphorical thinking is,
but also that much of our metaphorical thinking is
based on arbitrary conventions that aren’tpre-
served across cultures. Nietzsche contributed a
strange property of metaphor in “On Truth and
Falsity in their Extramoral Sense”:
What therefore is truth? A mobile army of meta-
phors, metonymies, anthropomorphisms: in short
a sum of human relations which became poetically
and rhetorically intensified, metamorphosed,
adorned, and after long usage seem to a nation
fixed, canonic and binding; truths are illusions of
which one has forgotten that they are illusions”.
3
Disciplines progress according to the strength of
their metaphors, and those metaphors are fated to
become so familiar that they transform into illu-
sions, if even thought of at all. Nietzsche adds that
in an earlier age, it was
language which has worked originally at the con-
struction of ideas; in later times it is science. Just as
the bee works at the same time at the cells and fills
them with honey, thus science works irresistibly at
that great columbarium of ideas, the cemetery of per-
ceptions, builds ever newer and higher storeys; sup-
ports, purifies, renews the old cells, and endeavors
above all to fill that gigantic framework and to
arrange within it the whole of the empiric world.
4
The scientific edifice will stretch past the sky like
an endless erector set but it is still built on a core
of metaphor. But what if the metaphors are inher-
ently limiting, or even counterproductive?
The problem the man of science faces is that ‘the
impulse towards the formation of metaphors, that
fundamental impulse of man’ withstands and is
even used to interpret the ‘regular and rigid new
world’ that comes from the pursuit of knowledge
and truth according to the scientific method.
Scientific ideas, Nietzsche explains, are constantly
confused by the construction of ‘new figures of
speech, metaphors, metonymies’ such that the
‘existing world of waking man’ is ultimately ren-
dered ‘motley, irregular, inconsequentially incoher-
ent, attractive, and eternally new as the world of
dreams is’.
4
Part of the problem inherent to this
marriage of metaphor and scientific knowledge is
that individual metaphors exist within ‘a whole
system of metaphorical concepts—concepts that we
constantly use in living and thinking. These expres-
sions, like all other words and phrasal lexical items
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in the language, are fixed by convention’.
2
The scientific disci-
plines use their own cosmologies of metaphor with which to
produce and disseminate understanding, and medicine’s central
pain metaphors that marshal a mobile army of truth are of
weapons and damage, as per Scarry, but also metaphors of neur-
ology that include doors, keys, wires and circuitry.
i
Pain was first codified by the International Association for the
Study of Pain (IASP) in 1979 as “an unpleasant sensory and
emotional experience associated with actual or potential tissue
damage, or described in terms of such damage”
5ii
. A single sen-
tence long, this abstraction cannot convey what pain is, what it
feels like. Textbooks that recount medical history often point
out that the definition includes the parameter of emotion,
taking pain back from the clinical, hyperphysiological viewpoint
of the 19th, 20th and 21st centuries. The discipline’s definition
is a negative one restricted to metaphors of damage. That this
definition is consistent with the concept of pain operating in
general society—pain as a negative experience—does not mean
it is an adequate definition, for as Lakoff and Johnson show, our
metaphors can work to increase or decrease understanding. It
may be that the popular discourse around pain—pain as nega-
tive experience as expressed by metaphors of weaponry and
damage—is, in metaphorical terms, the ‘wrong road.’ If pain
can only be negative, then pain will only be used for negative
purposes and have negative effects. This is an inherent obstacle
to recovery from painful conditions. What is lacking in the IASP
definition is the dissent of possibility, a description of transcend-
ent effects, of how this undeniably unpleasant experience has
useful results for individuals and for society. Perhaps the
problem is a chronological one, for acute pain is a message of
actual tissue damage, whereas chronic pain is usually pain signal
without damage. (Even so, the language used here—one of
‘damage’—implies a lack of value in the affected body part, a
state of affairs contested by the burgeoning field of disability
studies.) But the possible positivity of pain, and its metaphorical
roots in acute situations, is a subject that can be taken up in
another forum. For now, it is important to recognise that the
IASP definition is influential and provides the dominant meta-
phor for the whole branch of pain medicine
iii
and that when I
refer to pain I mean chronic pain.
What is often ignored by medical professionals is the part of
the IASP that defines pain as an ‘experience.’ In present-day
North America, pain is a clinical experience that is relegated to
medicine for alleviation. In The Culture of Pain, David Morris
asserts that “[t]he vast cultural shift that gives the story of pain
its hidden plot centres on the eradication of meaning by late
nineteenth-century science. . .[w]e are the heirs of the trans-
formation in medical thought whereby we think of pain as no
more than an electrical impulse speeding along the nerves”.
6
Medicine and the public use hegemonic metaphors to compre-
hend pain. Morris’ text proceeds to examine how an inherently
metaphorical understanding of pain absorbed by the larger
public came into effect. There are problems with this wholesale
relegation of pain to medicine and I will consider these pro-
blems at length in another forum. For now, the following
summary of pain theories and their bases in metaphor constitu-
tes a real narrative of progress. Textbooks like John Bonica’s
The Management of Pain, considered a standard in the field,
briefly narrate the history of pain medicine in a single chapter
before voluminously providing modern management princi-
ples.
7
In their abbreviated historical sections, such textbooks
present pain as moving from primitive to a sophisticated under-
standing. In anatomical, physiological and biochemical terms,
this is incontestable. Yet in a paradoxical way, the progress nar-
rative has been, qua Nietzsche, obliterated by the metaphor of
progress. Progress becomes the narrative, obscuring a truth
which I hope to show is one of vast, systematic and elaborate
oversimplification as encouraged by metaphorical understanding
that conceals its nature as metaphor. Though neurological meta-
phors have assisted with the accumulation of scientific knowl-
edge, their enshrinement as the means of understanding pain
has had a terrible cost. We think of pain in terms of nerves, but
nerves are not experience and nerves are not necessarily
emotion. Nerves are not pain.
The first well-formed pain theory on record was derived by
Aristotle (384–322 BC) who identified the affective component
of pain. His work forms the foundation of much current under-
standing of the topic, and pain textbooks routinely invoke
Aristotle’s concept of pain as ‘passion of the soul’ because his
definition corresponds with IASP’s modern definition that
includes ‘emotional’ experience. Yet pain textbooks provide the
briefest mention of the four quoted words, leaving out
Aristotle’s complex definitions of ‘passion’ and ‘soul.’ Pain text-
books move on from Aristotle to similarly microquote from the
humoral theory of Hippocrates, the next ancient theorist on a
short (and curiously variable) list. From there, Galen. Onward
to Descartes! There are a few other pain theories, but Aristotle’s
definition demonstrates the major problem inherent in the
extreme summary by medical textbooks. Receding knowledge
might be cited but is rarely understood, and it is the metaphors
knowledge relies upon that are important, not knowledge itself.
Book I of De Anima begins by providing a historical survey
on the topic of ‘soul.’ This is the text that sets out Aristotle’s
thinking about the nature of life. RD Hicks concluded from this
book that Aristotle believes that “the attributes of soul cannot
properly be separated from those of the body”.
8
In Book II,
Aristotle furthers his investigation by launching into his own
definition of ‘soul.’ In this foundational text cited by textbooks
as proof of Aristotle’s thinking on pain, pain is not a central
concern—it is instead a minor topic enfolded under a much
broader range of topics. Pain is really only theorised by Aristotle
in the second part of Book III within a moral framework. With
30 chapters, De Anima requires more than four words of
summary in order to understand what Aristotle truly means
when he writes on pain. Pain cannot be understood out of
context, including definitions of pain. Ironically, our underlying
neurological metaphors short-circuit understanding.
Part of this context comes in Book II when Aristotle sets out
the criteria for an organism to be called ‘alive’: (1) intellect, (2)
sense, (3) locomotion and (4) motion of nutrition, growth and
decay. He then moves to define what constitutes an animal: a
living thing that distinguishes itself from other living things like
i
As Lakoff and Johnson point out, humans “typically conceptualize the
nonphysical in terms of the physical–that is, we conceptualize the less
clearly delineated in terms of the more clearly delineated” (p. 59).
2
Even if it is never explicitly stated in contemporary texts as such, the
visual representation of cell membranes at the molecular level has a clear
wire/door appearance.
ii
The importance of Canadian contributions to the understanding of pain
cannot be underestimated. For example, the IASP definition was written by
Merksey, a former professor of Psychiatry at the University of Western
Ontario.
iii
That pain can have positive elements is a minority view in Western
culture. Though medical histories approve of the inclusion of emotion
in the IASP definition, they do not criticize the negative path
researchers, huddled around the definition, have taken. Following the
lead of medicine, culture has adopted medicine’s view of pain as
negative.
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plants on the basis of sense perception. This constitutes
Aristotle’s first serious mention of the senses. He mentions
touch first out of the five senses in order to further substantiate
what constitutes ‘ soul.’ Touch is mentioned to assist with
taxonomising life forms, not as a sense implicated in pain.
In Chapter 3 of Book II, Aristotle puts pain squarely within an
originating context of desire: “But all animals have at least one
sense, touch; and, where sensation is found, there is pleasure
and pain, and that which causes pleasure and pain; and where
these are, there also is desire, desire being appetite for what is
pleasurable”.
9
Aristotle links pain and pleasure together in a
moral framework. It should be clear at this point that the rereca-
pitulations of Aristotle by modern medical textbooks are quite
decontextualised. How Aristotle is represented in pain text-
books goes a long way to proving the inadequacy of the pain
textbooks as a group, for such texts constitutively reproduce
‘passion of the soul’ in what can be charitably referred to as
catachresis and less charitably as mere historical adornment.
If desire, pleasure and the good life entered into contemporary
medicine’s concept of pain, then our metaphors would not be
the same. As corollary, our IASP-mandated ‘ experience’ of pain
would not be the same.
One other thinker deserves mention in brief due to his influ-
ential scientific and metaphorical contribution to pain. Rene
Descartes (1596–1650)
iv
, taking his cue from Aristotle, devel-
oped his theory of dualism in The Passions of the Soul (1649).
The title and style of argument of this text are Aristotelian.
Descartes likened the body to a machine and wrote that the
mind is controlled by the soul, which he felt resided in the
pineal gland (in opposition to the accepted view in his day that
the soul resided in the heart). Descartes maintained that the
nerves of the body were acted upon by the pineal gland through
the medium of cerebrospinal fluid, a marked improvement over
Hippocrates’ humoral theory that suggested control over the
body comes from the brain as mediated by neural structures.
Descartes inaugurates the neurological metaphor for under-
standing pain, a development which reaches an apogee in the
modern day. Ironically, Descartes’ writings are densely meta-
phorical. Even his theory about pain perception is expressed in
metaphorical terms: he maintains that pain travels from site of
injury to the brain “just as, pulling on one end of a cord, one
simultaneously rings a bell which hangs at the opposite cord”.
10
As per Morris, a culture’s metaphorical system of nerves and
pain is born. But like Aristotle, Descartes’ thinking gets simpli-
fied over time and the complexity of pain is sidelined too.
Descartes is renowned as the great splitter of mind and body,
the great dualist, but this perception is actually a disservice to
his thought. Again, context is key, a fact literary scholar Jan
Frans van Dijkhuizen demonstrates while writing about repre-
sentations of pain in late mediaeval English literature. Consider
the passionate fusion of mind and body in Descartes’ six meta-
physical meditations wherein it is proved that there is a God and
that man’s mind is really distinct from his body:
[T]here is nothing that this my Nature teaches me more expressly
then that I have a Body, Which is not Well when I feel Pain […]
And by this sense of Pain, Hunger, Thirst, etc. My nature tells me
that I am not in my Body,asaMariner is in his Ship, but that I
am most nighly conjoyn’d thereto, and as it were Blended there-
with; so that I with It make up one thing; For Otherwise, when
the Body were hurt, I, who am only a Thinking Thing, should
not therefore feel Pain, but should only perceive the Hurt with
the Eye of my Understanding (as a Mariner perceives by his sight
whatever is broken in his Ship).
11
Clearly Descartes was not as absolute about the division
between mind and body as is commonly perceived: pain compli-
cates his otherwise strict dualism. Analysing the passage above,
Jan Frans van Dijkhuizen asserts that pain “throws into doubt
the very distinction between mind and body/matter which
(Descartes) has first attempted to construct, since it points to the
inescapable fact of human embodiment. Pain, more than any
other physical sensation, confronts us with the fact that we do
not just have bodies, but that we are our bodies”.
12
Writing that
his body and mind are ‘Nighly conjoined,’ Descartes understood
that pain complicates strict categories, making his pain concept
much like that of Aristotle and the IASP, but constituting—as
per the conventional narrative—an increment of progress. The
scientific process selects certain findings and metaphors to create
the narrative of progress, but the truth of our metaphors sug-
gests a much more fertile field before the husbandry. Pain was
and is more complex than our current metaphors allow.
Following Descartes, pain theorists included sensory and
affective experience in their formulations but these remain
abstract up to the present day. In the absence of real understand-
ing or knowledge, the physiology of pain receives exquisite
refinement instead. In the modern era, we talk about pain in the
language of science, but the language of science remains, at
bottom, the language of metaphor and ‘as if ’ formulations mas-
querading as authoritative knowledge. I bring the reader quickly
up to date by mentioning a few other pioneers in pain theory
and research in order to sketch in the basis of medicine’s neuro-
logical metaphors for understanding pain. In the 19th century,
major advances were made in pain theory predicated on a
greater understanding of neuroanatomy and neurophysiology.
Though not alone, Charles Bell, a prominent Scottish neuro-
physiologist, laid much of the groundwork for what would
eventually be known as specificity theory by writing in 1811
that
the external organs of the senses have the matter of the nerves
adapted to receive certain impressions, while the corresponding
organs of the brain are put in activity by the external excitement:
That the idea or perception is according to the part of the brain
to which the nerve is attached, and that each organ has a certain
limited number of changes to be wrought upon it by the external
impression.
That the nerves of sense, the nerves of motion, and the vital
nerves, are distinct through their whole course, though they seem
sometimes united in one bundle; and that they depend for their
attributes on the organs of the brain to which they are severally
attached.
13
Bell’s cold neuroanatomical descriptions, surgical induction of
lesions and elucidation of resultant effects constitute a different
kind of discourse in the Foucaldian sense—a medical, neuroana-
tomical and neurophysiological discourse. Bell’s writings dir-
ectly led to Johannes Muller’s ‘Doctrine of Specific Nerve
Energies’ from 1835, which is as follows: “The nerve of each
sense seems to be capable of one determinate kind of sensation
only, and not of those proper to the other organs of sense;
hence one nerve of sense cannot take the place and perform the
functions of the nerve of another sense”.
14
The presence of dis-
sectible structures creates ‘doctrines’ that are ‘specific’—the
iv
Descartes is considered the first ‘analytic scientist of neurophysiology’
by Uhtaek Oh, the revisionist editor of hard-science textbook
The Nociceptive Membrane. This is an example of how modern
discourses penetrate the older ones and claim them for their own as a
battle for primacy.
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medical discourse is presented as authoritative even though its
true knowledge at this point is vanishingly small.
Like all theories in any discipline, adherents to a given pain
theory privilege their theory, resulting in intellectually gladiator-
ial pain discourses that compete in an academic arena for
supremacy in terms of defining how to acquire knowledge. But
because every pain theory works in an arena, the fallacy of
supremacy is demonstrated. What is supreme is the medical dis-
course itself. By the term ‘medical discourse,’ I invoke
Foucault’s broad conception of discourse, including speech acts
and social acts performed by medical and paramedical personnel
that are directed and grouped around political and economic
institutions like medical colleges, hospitals and journals. This
discourse also includes the images used to represent pain and
the symbolic meaning that culture attributes to those representa-
tions. Clinical in nature, medical discourse decontextualises
experience in order to isolate pain as symptom and sign. In
medical discourse, pain is expressed within language that is fun-
damentally negative in tone and implication—pain as disability,
disorder and diagnosis. But what is truly powerful—the source
of medical power and the illusion of power—is that pain is a
problem misunderstood by neurological metaphors.
I begin this discussion of theory with the various theories that
fall under the general category of pattern theory. Pattern theory
was a prominent concept defined as “patterns of activation,
spatial or temporal, in neurons that do not necessarily have time-
locked responses to painful stimuli”.
15
This theory posits that
there is more to pain than the labelled line extending from stimu-
lus to brain. Rather, pain is signalled in a complex manner
through parallel neural networks and processing. Though pattern
theory has been around for over 100 years, it was elegantly
articulated in 1965 with the gate control theory of pain by Ron
Melzack and Patrick Wall, two researchers working at the
Montreal Neurological Institute. This revolutionary articulation
of theory—betraying reliance upon metaphor in the very name
of the theory with the use of ‘ gate’—was presented as follows:
We propose that (1) the substantia gelatinosa functions as a gate
control system that modulates the afferent patterns before they
influence the T cells; (2) the afferent patterns in the dorsal
column system act, in part at least, as a central control trigger
which activates selective brain processes that influence the modu-
lating properties of the gate control system; and (3) the T cells
activate neural mechanisms which comprise the action system
responsible for response and perception. Our theory proposes
that pain phenomena are determined by interactions among these
three systems.
16
Laurence Kirmayer, the James McGill Professor and Director
of the Division of Social and Transcultural Psychiatry at McGill
University, interprets the theory like this: “[t]he key insight was
the notion of central control of peripheral processes: that affer-
ent control occurs at many different levels”.
17
Note the com-
plexity of the gate-control construct as rooted in anatomy and
concept. What is proposed is not one wire connected to another
wire (ie, nerve A connects to centre B) but rather a multimodal,
regulated system. The gate-control theory created an experimen-
tally testable concept of pain that initiated a revolution in the
understanding and treatment of pain. Kirmayer adds that the
gate control theory “provided a natural conceptual framework
to begin to integrate cognitive, psychological and ultimately
social and cultural processes”.
17
As much of an advance as the
gate control theory was, it is no more complex than a metaphor
about policing a door. It is important to state this fact because
complexity is often explained through the use of metaphor to
provide understanding. What can be lost, what can seem illu-
sory, is the basis of understanding. The complexity remains as
science but the metaphor hides in plain sight as a commonplace.
Our inconspicuous metaphors control our understanding but
we are not aware of it. We amble through pain as unconscious
beasts (figure 1).
And, in particular, we rely upon visual metaphors as our
interpretive tools. Within the medical discourse, there is a
system of visual metaphors for pain. Such images are meant to
represent progress while ignoring their provenance as metaphor
due to the special nature of image—that of concretised truth.
Though images are intended to be a simplification of truth, con-
temporary schematic explanations of pain represent a hearken-
ing back to 19th-century specificity theory. Morris writes, “We
are the heirs of the transformation in medical thought whereby
we think of pain as no more than an electrical impulse speeding
along the nerves”.
18
We are the heirs, and we are in an import-
ant way re-innovators of this idea. Although the present deluge
of diagrams and textual explanations of pain don’t argue for a
return to specificity theory per se, they do pretend to an
immense knowledge of how one wire connects to another wire,
leaving out the affective dimension entirely. Mechanisms are
emphasised in medical discourse. ‘What is pain?’ is a difficult
question to answer, but opiate and GABA receptors can be iden-
tified, tested in experiments, and the results published in articles
rich with schematics and diagrams. In this way, the simple is
represented simply, demonstrating the secret and dangerous
power of visual representations that avoid images of human
beings in pain. Standing on the shoulders of schematics,
Figure 1 A schematic of gate control
theory. Adapted from Melzack and
Wall.
16
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medicine appears powerful and knowledgeable. Yet the sche-
matics are metaphors which perpetuate themselves to the detri-
ment of complex truth. Schematics are visual metaphors that
limit understanding because of extreme simplicity.
Pain medicine’s learning curve is a way to police the door to
understanding pain. To understand pain, one must first assimi-
late significant amounts of knowledge about basic neurophysi-
ology. The state of neurophysiological knowledge, as opposed
to pain perception, is advanced. Digesting basic explanations of
how nerves conduct electricity like ‘[n]eurons communicate by
producing electrical impulses called action potentials. Action
potentials are self-regenerative electrical signals that tend to
propagate throughout a neuron and along its axon. The action
potential is a depolarisation of about 100 mV’
19
leads to the
seductive inference that it’s not just electric impulse that’s con-
ducted, it is pain that is conducted. This inference is true in that
there are certain nerve fibres responsible for transmitting certain
kinds of pain. But it’s not true in that this signal is just that—a
signal. It isn’t pain. No nerve diagram with plus and minus
signs on either side of a line representing a membrane turns
knowledge into knowing (figure 2).
Who could look at such a diagram when in pain and say,
‘This is pain!’ Admittedly, no student looks to diagrams like the
one above to understand what pain is specifically. Yet the
unacknowledged metaphorical basis of the diagram (nerves are
wires) and the fact that the diagram is a basic building block
common in medicobiological texts, leads to the creation of a
powerful metaphor-based illusion. Much of the understanding
of pain gets relegated to a diagram such as this one. Although to
understand pain, one must learn nerve signalling, one should
also recognise that nerve signalling serves as the physiological
basis of a metaphorical system. There is an illusion that more is
known as the state of current knowledge is vast in terms of intri-
cate mechanisms. Distortions occur among those without train-
ing and even those with training, because of the nature of
scientific progress identified by Nietzsche. There is more to pain
than can be metaphorically illustrated by ‘nerves’, but a neuro-
physiologist too can quickly forget what is only partially appre-
hended by the hegemonic metaphors. For example, incredibly
detailed mechanistic explanations of pain add little to the IASP
definition of pain. The following words from the domain of
molecular biology prove the point:
The magnitude and nature of leak conductance determines mem-
brane resistance and the impact a generator current will have on
Figure 3 The spinothalamic pathway. Adapted from Somatic Sensory
System (http://www.rci.rutgers.edu/~uzwiak/AnatPhys/
ChemicalSomaticSenses.htm).
Figure 4 An illustration by Descartes to show fire ‘pulling’ a thread.
Retrieved from Wikipedia (http://en.wikipedia.org/wiki/History_of_pain_
theory). Original illustration appeared in Descartes’ Treatise of Man
(1664).
Figure 2 A schematic of action potential propagation. Adapted from
Review of Membrane and Action Potentials (http://www.life.umd.edu/
classroom/bsci440/higgins/lecture2.html).
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the membrane potential. . .[g]iven the fact that there is consider-
able variation in the biophysical properties of Na+ channels
depending on which (alpha) and (beta) subunits are present, the
relative density of these subunits will have a significant impact on
action potential threshold.
20
Knowing which subunit communicates with another is
important at the level of possible intervention sites for pharma-
cological therapy, but this knowledge does not augment the
IASP definition. Yet such is the frontier of pain research, a per-
petual spelunking of microdetail that fills the pages of the most
prestigious journals. Pain researchers investigate the domain of
receptor, ion and protein fold. Molecular biology, neurophysi-
ology and reproductive neurobiology are the ascendant medical
discourses of pain, and they are intoxicating precisely because of
their reductive power. The danger—and, I argue, implicit
message—is that one doesn’t need to bother with politics, reli-
gion or power when viewing such diagrams.
But one does. In Descartes’ day and for some time before
that, Christianity provided the Western world with a hegemonic
pain discourse other than the medical. By building an iconog-
raphy around Jesus Christ, Christianity used Christ’s last days
after re-entering Jerusalem (tellingly titled the ‘Passion’ in
English) in a framework of human suffering—that pain serves as
a conduit to God, that suffering intensifies one’s relationship
with the maker. This relationship was presented as a pleasurable
and even sexual one. Albeit problematic, the Christian attitude
towards pain is more positivist than that of the clinic. And
ignoring politics in the conceptualisation of pain is to ignore the
maimed, war-torn world that pain makes.
Mechanistic discourses are possibly inferior than religious
ones in terms of articulating pain because of their inherent lack
of meaning. When modern-day Rene burns his finger, he knows
that physical pain is the result of nociceptors sending a signal
from the periphery to the brain, as well as top-down processes
modulating that same signal, as well as (perhaps) a God oversee-
ing the process. But Rene also knows much more that science
doesn’t know yet: Rene knows he can reach for certain medica-
tions that will give him analgesia (he knows he can thank the
mechanistic discourse for that) but if he wishes to make sense of
his pain, his knowledge of the spinothalamic tract won’t help
him. If the fire was due to poor enforcement of building codes,
or Rene lost his job due to a global financial crisis, turned to
state-taxed alcohol in order to numb his pain, and inadvertently
left a cigarette burning in bed, resulting in extensive burns. . .
knowing wire A leads to wire B won’t help Rene cope on the
burn unit. He has a problem meaning, not a problem of neur-
ology. Meaning is inherently bound up in metaphor and Rene
needs better metaphors to reflect the complexity of his plight.
To demonstrate the rootedness of this problem of metaphor, I
provide a specific series of diagrams that are metaphors mas-
querading as hard knowledge. Contextualisation in the form of
narratives can expose the reductive nature of visual metaphors.
Visual metaphors are the sine qua non of the medical pain dis-
course of the late 20th century onwards because they are more
‘concrete’ than those channelled by words. Consider figure 3,a
diagram documenting the pain pathway as it relates to thermal
sensation, one like it included in every textbook of pain (and
ubiquitous on the internet):
The pedigree of the above diagram extends far back in
history. Because the diagram shows a peripheral stimulus
sending a signal to central structures (a wire system), the
diagram is conceptually as simple as Descartes’ thread running
from the skin to the brain:
In figure 4, pain caused by intense heat ‘pulls the string’ of a
nerve causing the tethered brain, now recognising the sensation
of pain, to send a signal to the foot to withdraw. This
call-and-response model chimes with contemporary diagrams of
cell membranes, including the amorphous balls in University of
Figure 5 Diagram from p. 2–4 of Allan Fein’s Nociceptors and the
Perception of Pain, 2012.
Figure 6 A schematic of ion channels. Adaptedfrom Uhtaek.
21
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Connecticut professor Alan Fein’s Nociceptors and the
Perception of Pain (figure 5):
No more than a simple picture matching a simple concept,
Fein’s ‘door’ to the outside world opens in response to a stimu-
lus. We remain in the metaphorical system of gate/door. What if
the representation is more complex, such as one informed with
contemporary neurophysiology?
The same ideology is at work in this diagram. At the level of
superficial inspection, this diagram is more complex than Fein’s,
but on closer inspection it is just another wire/door metaphor
with more elaborate knobs and tubes. Indeed, acronyms become
the door’s textual keys. Perhaps the image of the synapse comes
closer to communicating pain experience than the spinothalamic
tract diagram, for the synapse metaphorically represents the real
gap between knowledge and knowing. But if metaphor is what’s
required to bridge the gap between knowledge and knowing,
then science must be honest about its fundamental basis in
metaphor.
The obvious riposte is that images like the one above are not
meant to represent pain in total at all, that instead these figures
demonstrate an infinitesimal piece of the puzzle of pain. But
medicine focuses on these details to the detriment of the puzzle.
Figure 7 Plate I from Charles
Darwin.
22
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The puzzle can never be solved because of the pursuit of parts.
Elucidating components is simpler than understanding the
whole. What’s missing in these diagrams is the complex truth.
The caption features a pile-up of acronymic explanations. To
the non-specialist, images like these would seem like a perpetual
wash, one spilling into the next that’s meant to diagrammatise
obscure molecular concepts. Figure 6 replicates the Cartesian
human machine receiving some signal or other through means
of doorbells and wires, albeit in a refined way. Yet the diagrams
are no more informative than Descartes.
Consider the photographs included in Charles Darwin’s The
Expression of the Emotions in Man and Animals (1872) where
photographs of infants in pain are included. Looking at these
faces, are we not staring at (or in) the face of pain (figure 7)?
Contemporary science has offered an explanation of what is
happening within the pictures and by the viewer of those pic-
tures. Validated pain face scales quantify the level of pain experi-
enced by the sufferer, and the work of Damasio, Tranel and
Damasio has found that peripheral nociceptors connect to the
thalamus, a structure that regulates emotional content. In turn,
the thalamus sends a signal to the fusiform gyrus to effect con-
sequent facial expression.
23
Somehow the image of an infant in
pain—knowing the infant is in pain—supersedes such scientific
knowledge. An observer is moved by what she sees through an
affective response. This interior drama matches the exterior one
and is an important part of the narrative.
Medicine uses negative (damage/weapon) and neurological
metaphors to the detriment of people in pain. How the uncer-
tain and hypothetical nature of metaphor is elided in favour of
the illusion of authority and competence has done pain sufferers
a disservice. By accumulating mountains of mechanistic detail,
the affective component has been lost as has the unstable nature
of the understanding provided by science. Although negative
and neurological metaphors explain pain to some extent, they
are not sufficient. Other metaphors are necessary, as is realising
the contribution of narrative to the study of pain. Pain is more
than neurological metaphor. Pain is what we say it is over time.
Pain is also the context in which we feel pain, and that context
need not be a clinicoapocalyptical one of damage, weaponry or
live wires.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Open Access This is an Open Access article distributed in accordance with the
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Pain as metaphor: metaphor and medicine
Shane Neilson
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