Philosophical Review
Wright on Functions
Author(s): Christopher Boorse
Source: The Philosophical Review, Vol. 85, No. 1 (Jan., 1976), pp. 70-86
Published by: Duke University Press on behalf of Philosophical Review
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The Philosophical
Review,LXXXV, 1 (January 1976)
DISCUSSION
WRIGHT ON FUNCTIONS
CHRISTOPHER BOORSE
A TTRIBUTING functionstofeaturesoforganismsisa favoriteactivity
The problemof analyzing
1A~of biologists.
thesefunction
statements
has
generateda livelycontroversy,
to whichthemostcarefully
defendedcontributionto date is surelythatof LarryWright.'Wrightalso offersa
comprehensive
critiqueofrivalviews.Althoughthiscritiqueseemslargely
successful,
therearereasonsforthinking
thathispositiveproposalremains
forceshown
unsatisfactory.
Wright
arguesthata certainsortofexplanatory
byfunction
statements
is thecentralelementin theirmeaning.In particular,he holdsthatthefunction
ofa traitisthatone amongitseffects
bywhich
itspresencemaybe explained.I wishtoarguethatthisetiological
approach
is inferiorto a simplearticulation
of an older idea: thata functionis a
contribution
toa goal.In thefirst
sectionI willdiscussWright's
proposal;in
thesecondI willdefendthecompetinggoal analysis.
I
is thatto attribute
maincontention
a function
to a traitis tosay
Wright's
aboutitsetiology,
or causal history.
he suggests:
something
Specifically,
ofX is Z means
The function
(2) (a) X is therebecauseitdoes Z,
(b) Z is a consequence(or result)ofX's beingthere[p. 161].
The functionof gillsin fish,for example,is respiration.Accordingto
Wright,thatis because the historical
developmentof gillstookplace by
naturalselectionin favorof theirrespiratory
effect.Respirationis the
function
ofthegillsbecauseitis thateffect
oftheirpresencebywhichtheir
presencemaybe casuallyexplained.
threecrucialcondiWrightarguesthatthisetiologicalanalysissatisfies
distinction
tionsof adequacy.First,it providesforthe function-accident
(pp. 141, 165). Manyof the effectsof organsand processes,however
that
do notseemtobe theirfunctions.
beneficial,
Althoughitisconvenient
1 Larry Wright, "Functions," PhilosophicalReview, LXXXII
Parentheticreferencesin the text are to this article.
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(1973), 139-168.
WRIGHTON FUNCTIONS
noses can support eyeglasses, that is not the functionof noses (p. 148).
Accordingto Wright,thisis because the supportingof eyeglassesplayed no
role in the evolutionaryetiologyof the nose: the nose is not therebecause it
supports eyeglasses. Second, the analysis applies univocallyto organisms
and artifacts(pp. 143, 164), as competinganalyses frequentlydo not. We
may say that the functionof a sweep-second hand on a watch is to make
seconds easier to read. This means, Wrightthinks,that the sweep-second
hand got into the design by virtueof having thiseffect(p. 158). Withboth
organismsand artifacts,a functionalpart is therebecause of the functionit
performs.Finally,Wright'sanalysis shows why functionstatementshave
inherentexplanatoryforce(pp. 154-156). Since theyinvolvetheclaimthatX
is therebecause it does Z, theyconstituteanswersto the question "WhyisX
there?"
These three adequacy conditions are extremely plausible ones, and
Wright'sexplicitstatementof them is a real advance. But the analysishe
proposes to satisfythem raises serious difficulties.
We maybeginbynotingitstrivializingeffectupon a thesisof evolutionary
biology. Consider the claim that in the evolutionof organisms,functional
traitstend to persistand nonfunctionalones tend to disappear. On Wright's
analysis the statement
X is there because it has a function
receives the translation
X is there because it has a consequence because of which it is there.
This translationis not strictlya tautology;logicallyspeaking,X could get
into an organism and remain withoutdoing anythingat all. But Wright's
renderingis much closerto a tautologythanone expectsfroman apparently
is that"X is there
substantiveremark.From a differentangle, the difficulty
because it has a certain function"has been made synonymouswith"X is
there because it has a certain effect."This result is peculiar if, as Wright
insists,"function"and "effect"are not synonymous.On his account thereis
clear content in a specificstatementlike "The heart is there because it
pumps blood" or "The stomachis therebecause itdigestsfood." But thereis
almost no content in the generalization that the presence of an organic
charactermay be explained by itsfunction.For thisgeneralizationreduces
to the statementthatorganiccharactersmaybe explained bythingstheydo
by which they may be explained. One could wish that explanatoryforce
mightbe accorded functionstatementsat a lower price.
A second difficulty
withWright'sanalysisis thatitis clearlyincompleteas
itstands. His formulationof theetiologyclause-"X is therebecause itdoes
Z" -is quite general, as is dictated by the aim of univocalitybetween organismsand artifacts.The onlyrestrictionon the clause is that"because" is
to be taken "in its ordinary ... causal-explanatorysense" (p. 157). Thus
one would assume thatregardlessof whetherorganismsor artifactsare in
question,any ordinarysortof etiologicalexplanation ofX byX's effectswill
support a functionstatement(cf. p. 164). But thisis not the case. The fact
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CHRISTOPHER BOORSE
failsto emerge in Wright'sdiscussionlargelybecause all his organic examples involve one patternof etiological explanation and all his mechanical
examples another. When organisms are in question, all cases are of an
evolutionarysort: the traitX arises in the firstplace by chance and then
survivesbyvirtueof doing Z. Withartifacts,however,Wrightconsidersonly
etiologicalexplanationsthatappeal insteadto theintentionsof thedesigner.
As soon as one examines cases wherethesepairingsare reversed,itbecomes
clear thatthe restrictionsto specificetiologypatternsmust be regarded as
part of the analysisitself.
Consider firsta counterpart to evolutionaryetiology for an artifact.
Suppose thata scientistbuilds a laser whichis connectedbya rubberhose to
a source of gaseous chlorine. Afterturningon the machine he notices a
break in the hose, but before he can correctit he inhales the escaping gas
and fallsunconscious.Accordingto Wright'sexplicitproposal, one mustsay
thatthe functionof thebreak in thehose is to release the gas. The release of
the gas is a resultof the break in the hose; and thebreak is there-that is,as
in naturalselection,itcontinuestobe there-because itreleasesthegas. If it
did not do so, the scientistwould correct it. This and similar examples
suggest that Wrightwill have to insiston the intentioninterpretationfor
artifacts.Conversely, consider an intentional etiology for a trait of an
organism.A man who is irritatedwitha barkingdog kicksit,breakingone
leg, withthe intentionof causing the animal pain. The dog's pain is a result
of the fracture,and the fractureis therebecause itscreatorintendsitto have
thatresult.Yet I doubt whetherWrightwould wishto say thatthe function
of the fractureis to cause the dog pain. So in parallel fashionone suspects
thatonly the evolutionaryinterpretationof "X is therebecause it does Z" is
supposed to be relevantto organisms.
These examples suggestthatWright'sanalysisought to be revisedinto a
disjunctionof specificetiologyclauses for organisms and artifacts:
The functionof X is Z means
(a) (1) X occurs in an organism and the presence of X may be
explained by its doing Z according to patternI, or
(2) X occurs in an artifactand the presence ofX maybe explained
by its doing Z according to pattern II; and
(b) Z is a consequence or resultof X's being there.
Exactlywhat patternsI and II should be is not clear fromWright'sdiscussion and would have to be workedout in detail. Such a revisionmakesithard
to call the analysis univocal between organismsand artifacts.But a more
importantobjectionis thatthereare counterexampleswithineach domain
to the view that any such etiologyis what gives a traitits function.
Let us take the case of artifactsfirst.Wrightmakes itclear thathe regards
the intentionsof the designer as centralto determiningthe functionsof an
artifact'sparts.In fact,these intentionsare not even required to be successful.Wrightsaysof a brokenwindshield-washerbuttonthatitsfunctionis to
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WRIGHTON FUNCTIONS
activatethe washer even though the washer never gets activated(p. 158).2
To see why this curious ruling is unsatisfactory,one need not dispute
whetherX can "do Z" under these conditionsin more than a Pickwickian
the analysisbecomes flatlyequivosense. For if pure intentionis sufficient,
cal. Effectsthatare onlyintended cannot figurein any etiologiesat all. But
this defect could easily be remedied by adding the requirementthat the
intentionsin question be successfuland that theirsuccess induce the designerto continuethe part in the machine.The revisedthesiswould be that
the functionof a partof an artifactis thatactual resultof itspresence which
the designer intended. In point of fact,however,such intentionsare cerforZ to be the function
tainlynot necessaryand perhaps not even sufficient
of X.
Such intentionsare not necessary because parts of artifactsmay have
functionswholly unknown to their makers. Many ancient mechanisms
achieved theirdesired goals withoutbeing understood by the people who
built them.The followingquotation froman articleon brewingin no way
strainsthe ordinaryusage of "function":
ofyeastas a living
years[1838-1858]therecognition
In thesucceedingtwenty
inalcoholicfermentabutitsexactfunction
becamemorewidespread,
organism
tionremaineda matterof controversy.3
As currentlyunderstood,the actual functionof yeastin fermentationis to
produce enzymeswhichcatalyzethe conversionof sugar to carbon dioxide
and alcohol. Presumably,then,thathas alwaysbeen the functionof yeastin
brewingdevices. It did not suddenlyacquire thisfunctionwiththeadventof
chemicaltheory.But brewerswithno knowledgeof enzymescannot intend
their yeast to produce them. Similarly,the functionof wood ash was unknownto ancientsoapmakers and the functionof the waterin a Leydenjar
to Franklin.Yet each of thesecomponentshad a definitefunction.Wright's
analysis can handle these cases only by saying that brewing,for instance,
would not have been popular enough to continue in existenceif yeastdid
not have catalyticaffects,and thatin thissense the yeastis there because of
its catalysis.But such an appeal to the survivalof a part via unintended
effectsis exactlywhat gave the wrong answer in the case of the chlorine
laser. A differentsolutionwillbe suggestedin the next section: thatsecreting enzymesis the functionof the yeastbecause thatis theiractual contribution, known or unknown,to the brewers' goals.
2
Wright'scommentson thisexample suggestthat he sees the designer's original
intentionsalone as determiningthe functionof a part, regardless of what later
intentionspeople mayhave about itduringthe restof itshistory.But his treatmentof
the safety-regulationscase (pp. 167-168) makes later intentionsrelevant, too. A
precise version of the clause for artifactswould have to state whose intentions
count-e.g., whetherthe designer's,the user's, or both-and at what times.
3 W. E. Trevelyan, "Fermentation,"Encyclopaedia
Britannica(1971), 9, 187.
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CHRISTOPHER BOORSE
to give partof his artifacta
Conversely,is a designer'sintentionsufficient
function?Consider firstthe positionadopted byWrightthatpure intentions
can make Z the function of X independently of whether Z is actually
produced. On thisinterpretationa partwhichonce acquires a functioncan
never lose it after the designer finisheshis work. This ruling creates a
peculiar divergence in the treatmentof artifactsand organisms. Let us
imagine thatan air conditioneris designed witha special filterforremoving
a certain atmosphericpollutantA, and that eventuallythis pollutantvanishes fromthe air. Even many years afterthere is no A in the air, Wright
would apparentlysay thatthe functionof the filteris to filterout theA. It
seems more naturalto hold thatalthough the filterused to have a function,
it is currentlynonfunctional.That is exactly what we do say, and what
Wrightthinkswe should say,about the appendix (p. 168). This divergence
would be eliminatedby our additional requirementthatfunctionalpartsof
artifactsmust succeed in performingtheir intended functions.But it is
unclear that even successfulintentionsconfer functionson their objects.
One oftenhears the hood ornamentson luxurycars described as nonfunctional. This statementis difficultto explain on Wright'sanalysis.A hood
ornamentdoes do somethingthe designerintendsitto do -namely, create
an impressionof opulence -and itis therebecause it does so in exactlythe
same sense as any otherpartof thecar. Again one is inclinedto adopt a goal
analysis:hood ornamentsare nonfunctionalin thattheymake no contribution to a contextuallydefinitegoal-that is, transportation-associated
withthe use of the car. It is difficultto see how else to distinguishintended
effectswhichare functionalfromthose whichare nonfunctionalexcept by
appealing to an implicitgoal. At anyrate,we have seen thatintentionsabout
the parts of artifactsare not necessaryfor them to have functions,and so
Wright'sanalysisis unsatisfactoryeven in the modifiedform.
Let us now turn from artifactsto organisms. My firstcriticismof the
etiologicalinterpretationof biologicalfunctionstatementsis thatitis historicallyimplausible.The modern theoryof evolutionis of recentvintage;talk
of functionshad been going on for a long timebefore it appeared. When
Harvey,say,claimed thatthe functionof the heartis to circulatethe blood,
he did not have natural selection in mind. Nor does this mean that preevolutionaryphysiologistsmust thereforehave believed in a divine designer. The factis that in talkingof physiologicalfunctions,theydid not
mean to be makinghistoricalclaims at all. They were simplydescribingthe
organizationof a species as theyfound it.This approach to physiologyis still
the standard one. Even today physiologicalfunctionstatementsare not
usually supported by, or regarded as refutableby, evolutionaryevidence.
Suppose we discovered, for example, that at some point the lion species
simplysprang into existenceby an unparalleled saltation.One would not
regard this discoveryas invalidatingall functionalclaims about lions; it
would show thatin at least one case an intricatefunctionalorganizationwas
created by chance. Given a littleknowledge about what happens inside
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WRIGHTON FUNCTIONS
mammals,itis obvious thatthe functionof the heartis to circulatetheblood.
That is what the heart contributesto the organism's overall goals, rather
then itsweightor itsnoise. But it cannot be obvious in any strictsense that
the hearthad an etiologyin whichthiseffectratherthanthe othersplayed a
role. Nothingabout the etiologyof the heart is obvious on inspectionat all.
The reason Wrightand othersmissthispoint,I think,is thattheyassume
that the point of a functionstatementis always to give a certain kind of
explanation discussed by philosophers of science. Function statementsdo
often provide an answer to the question "Why is X there?,"and it is this
explanationpatternthatHempel called "functionalexplanation."4There is,
however,anothersortof explanation using functionstatementsthathas an
equal claim to the name. This sort answers the question "How does S
work?,"whereS is the goal-directedsystemin whichX appears. Withsome
misgivings,I shall call such an explanation an "operational explanation." It
is operationalexplanation,not the evolutionarysort,withwhichphysiology
has traditionallybeen concerned. Confronted withinordinatelycomplex
organisms that achieve certain goals in a remarkablerange of conditions,
physiologistsset out to studythemas one would studyan alien artifact;that
is, by determiningwhat contribution,ifany,each part makes to the operationof thewhole. Anypossibilityof accountingfortheoriginof thesepartsis
a very recent one. Wrightis surelyjustified in insistingthat an adequate
analysisof functionstatementsmustexhibittheirrelationto the explanationstheysupport.But itis also an adequacy conditionthattheirsupportof
both sortsof explanation be allowed for,and his analysisdoes littleto show
whyfunctionstatementsare of use in operational explanation.5
ActuallyWright'saccount has the appearance of biological plausibility
only in so far as some veryspecificreferencesto evolutionarymechanisms
are thoughtof as writteninto it. Consider some counterexamples to the
formulationhe explicitlypresents. A hornet buzzing in a woodshed so
frightensa farmerthathe repeatedlyshrinksfromgoing in and killingit.
Nothing in Wright'sessay blocks the conclusion that the functionof the
buzzing,or even of thehornet,is to frightenthefarmer.The farmer'sfright
is a result of the hornet's presence, and the hornet's presence continues
because ithas thisresult.By failingto make any requirementthatfunctions
benefittheir bearers, the analysis also creates unwanted functionsof the
followingsort.Obesityin a man of meager motivationcan preventhimfrom
exercising.Although failure to exercise is a resultof the obesity,and the
4Carl G. Hempel, "The Logic of FunctionalAnalysis,"inAspects
ofScientific
Explanation(New York, 1965), pp. 297-330.
5 Wrightmentionsand rejectsthe idea thatfunctionstatements
answer the question"What'sitgood for?"(p. 155). This question is not the one I have in mind.To ask
whata thingis good foris differentfromaskinghow itcontributesto the goals of the
systemin whichit appears. In any case, Wright'sapparent presumptionthatthereis
only one kind of functionalexplanation is unwarranted.
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CHRISTOPHERBOORSE
obesitycontinues because of this result,it is unlikelythat preventionof
exercise is itsfunction.These cases suggestthatWrightmustsay explicitly
that the functionof X is Z only when the presence of X in a species has
resulted from selection pressure deriving from Z. But this alone is not
enough. An organX once establishedbyselectionpressurederivingfromits
effectZ may cease to be functional,as did the appendix, if a change in the
restof the organismor in the environmentrendersZ useless. To cope with
such cases, one mustinsistthatfunctionaltraitscreate selectionpressurein
the present as well as the past.
Instead of attemptingto findsome preciseetiologyclause fororganisms
to cover all problematiccases, one would do betterto realize thatfunction
statementsin physiologydo not carryevolutionarycontentat all. As something like a knockdown argument for this view I propose the following
hypotheticalcase. Suppose that the penile urethra had evolved firstas a
sperm conductor, the evacuation of urine being accomplished by other
means. In time,the rest of the organism then evolved in such a way that
urine came regularlyto be evacuated through the urethra as it is in our
species. Here we have a case where a fullyestablishedorgan acquires a new
functionwithoutalteringitsfeatures.And in such a case thereis no sense at
all in which the organ is there because it performsthe new function.The
urethrawas establishedin its finalformbefore the new functiondevolved
upon it, and would have survivedin this formhad it never acquired the
functionof evacuating urine. Now Wrightsays that given his analysis of
"The functionofX is Z," the proper analysisof "A functionofX is Z" would
be thatXis therepartly
because itdoesZ (p. 166). It is indeed hard to see what
other suggestion would be plausible. But in our hypotheticalcase the
urethra is not there even partlybecause it evacuates urine. Nevertheless
thereis no doubt thatthisremainsa functionof the urethra.Such multiple
functionsare no problem fora goal analysis:regardlessof the evolutionary
details, which physiologistsdo not usually know anyway,the urethra has
both of these functionsbecause both are standard causal contributionsto
the organism's over-all goals.
We may now conclude our critiqueof Wrightby suggestinga furthertest
for analyses of functionstatementswhich his account failsto meet. As he
pointsout (p. 139), functionalterminologyoccurs in various kindsof statementsbesides "The functionofX is Z" and "A functionofX is Z." One may
this
say that the nose functionsas an eyeglass support, or that it performs
function,whiledenyingthatsupportingeyeglassesis theor a functionof the
nose. Wrightcalls these and other usages "peripheral" (p. 139) or "quasifunctional"(p. 141). It seems less tendentious to call them simply"weak
functionstatements."Other thingsbeing equal, itis surelya pointin favorof
any analysisof strongfunctionstatementsif it lets us exhibita connection
between them and the weak varieties. Whatever the meaning of strong
functionstatementsis, one may expect it to support some explanation of
whythe term"function"seems appropriate in talk of "performinga func-
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WRIGHTON FUNCTIONS
tion" as well.
Wright'scomments on weak functionstatementsdo not show how his
analysiscan meet this test. He says:
useful'
does something
byaccidentratherthandesign,... we
Whensomething
signalthedifference
bya standardsortof"let'spretend"talk.Insteadofusing
theverb"tobe" or theverb"tohave,"and sayingthethingin questionhassuch
"funcwe use theexpression
and sucha function,
or sayingthatis itsfunction,
as a bulletshield,or the
tioningas." We mightsay thebeltbucklefunctioned
or thesweephandfunctions
as divineintervention,
as a dust
blowoutfunctioned
at all [p. 147].
brush.Canfield'sanalysisdoes notembracethisdistinction
What is puzzling about this explanation is that the idea of usefulness
nowhere appears in Wright'sanalysis,although it does in Canfield's. For
is a certainsortof etiology.But in the
Wrightthe essence of functionality
"functioningas" examples he gives,nothingwhateverabout the etiologyof
the beltbuckle,or the blowout,or the sweep hand is relevantto theiruseful
effects.It remainsobscure whyin the world we mightneverthelesswishto
"pretend" that their etiology was of the right sort to justify functional
language. If the pretenseis made onlywherea traithas usefuleffects,thatis
some argumentfora connectionbetween functionsand usefulness.Let us
now see how a goal analysis can explain this feature of weak function
statementswithoutobliteratingthe distinctionbetween the weak and the
strong.
II
One of the unquestionable virtuesof Wright'sanalysis is that his root
concept, "causal history,"offerssome hope of covering the vast range of
contextsin which functionstatementsappear. Besides the organismsand
mechanismsdiscussed by the literature,we also speak of the functionsof
words in sentences,signatureson wills,figuresin paintings,and so on. But
such breadth can also be achieved in anotherand less costlywaybyappealing to the notion of a goal. In every context where functional talk is
appropriate,one has also to do withthe goals of some goal-directedsystem.
It would be a mistaketo restrictthe analysis to some particulargoal like
"reproductive fitness"(Ruse) or "usefulness" (Canfield) or "the good"
(Sorabji).6 Any goal pursued or intended by a goal-directedsystemmay
serve to generate a functionstatement.Functionsare, purelyand simply,
contributionsto goals.
Since the objects of functionalascriptionwe have been discussing-that
6 See Michael Ruse, "Functional Statementsin Biology,"Philosophy
of Science,38
(1971), 87-95; John Canfield,"Teleological Explanations in Biology,"BritishJournal
of Science, 14 (1964), 285-295; and Richard Sorabji, "Function,"
for thePhilosophy
PhilosophicalQuarterly,14 (1964), 289-302. Ruse argues that functionstatementsdo
not entailanythingabout goal-directedness.His argument,however,uses a function
statementabout a goal-directedsystem(a dog). A more convincingargumentwould
be to present a functionwhich does not contributeto some system'sgoals.
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CHRISTOPHER BOORSE
is, organismsand artifacts-are mechanisms,it is causal contributionsto
goals withwhichI willbe concerned.This notionof a causal contribution,or
contributorycause, has come to seem unnecessarilyobscure since Nagel's
unhappy referencesto necessaryand sufficientconditions.7It is true that
but need not even be necessary
causes are not onlyinsufficient
contributory
fortheireffects.The pumping of the heart maybe a contributorycause to
thecirculationof theblood withoutbeingessentialto it,sincecirculationcan
occur by artificialmeans. But thisdoes not mean the idea of a contributory
cause should be abandoned, any more than any other ordinary causal
concept forwhich one lacks a precise analysis.For purposes of discussing
teleology,we are clear enough whatitmeans to say thatthe heartis helping
to cause thecirculationof theblood, even ifa heart-lungmachineis readyto
switchon at a moment's notice. We know well enough when a house is
runningoffthe power company ratherthan itsemergencygenerator.With
Ruse,8 one may say that heart action is contributingto circulationwhen
circulationis occurringby, or via, heart action, and let it go at that.
On the other hand, the notion of goal-directedbehavior,when applied
outside therealmof intentionalaction,looks more likea theoreticalconcept
of biologyto be explicated according to convenience.Differentaccounts of
thatagree extensionallyonly
it willyield differentanalysesof functionality
on clear cases of functions.At any rate, the notion of goal-directednessI
shall employ is a slightrevisionof Sommerhoff's.9Sommerhoff'scomplicated account, like those of Braithwaite and Nagel,10 is guided by the
followingidea. To say thatan actionor processA is directedto the goal G is
to say not only thatA is what is required forG, but also thatwithinsome
in whatever
range of environmentalvariationA wouldhave beenmodified
way was required forG. For example, capturinga bird maybe the goal of a
Ernest Nagel, The Structure
of Science(New York, 1961), p. 403.
Ruse, op. cit.,p. 88.
9 The most extended discussion is G. Sommerhoff,AnalyticalBiology(London,
1950). A helpfulsupplementis "The AbstractCharacteristicsof LivingOrganisms,"
in F. E. Emery(ed.), Systems
Thinking(Harmondsworth,1959). Sommerhoffdoes not
encounter the problem of the exploding fishwhich Lehman raises against Nagel
(Hugh Lehman, "Functional Explanationin Biology,"Philosophy
ofScience,32 [1965],
5). The case involves a deep-sea fishthat, once displaced upward, undergoes an
involuntaryexpansion whichcauses itto continuerisinguntilitbursts.At no stageof
thisprocess,according to Sommerhoff'sdefinitions,is the fishgoal-directedtoward
bursting(cf.pp. 93-94 and 54-55 ofAnalyticalBiology.)
For itis nevertruethathad the
externalpressurebeen differentat some level,the "behavior"of the fishwould have
showna modificationrequired forthe"goal" of bursting.Furtherdefenseagainstthis
example is provided bythe revisionof SommerhoffI suggestin n. 15. My solutionto
the problemof heartsounds (Lehman, op.cit.,pp. 5-6) willbecome clear near the end
of thispaper; itis thatthe sounds make regularcontributionto the goals considered
by physiology.
10R. B. Braithwaite,Scientific
Explanation(New York, 1960), pp. 328 ff.;Nagel, op.
cit.,pp. 547-548.
8
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WRIGHTON FUNCTIONS
cat'sbehaviorin so faras thisbehaviornot onlyis appropriateforcapturing
a bird but would also have been appropriatelymodified if the bird had
behaved differently.
1 require changes in thisaccount.
Two difficulties
mentionedbySchefflerl
Presumablya cat whichwaitsbyan emptymousehole may have the goal of
catching a mouse; but it is hard to see how any behavior can literallybe
required for catchinga nonexistentmouse. The cat's behavior can, however,fairlybe called appropriate to catchinga mouse: itis, forinstance,the
kind of behavior thatleads to catchingmice when theyare there. And this
Schefflermentions,
answer seems sufficient
except forthe second difficulty
the problem of multiple goals. In the presence or absence of a hidden
mouse, the cat's behavior may be equally appropriate to catchinga bowl of
cream -grant thisforthesake of argument.Furthermore,thecat maybe so
conditioned thatin environmentsincluding a bowl of cream it would take
it seems to make sense to say that
appropriate steps to get it. Yet intuitively
mice and not cream are the cat's goal.
I see no way to solve this second problem without abandoning Sommerhoffs ideal of a black-box analysis of goal-directedness.One might
thinkthatthe cat's goal is mice ratherthan the cream because one believed
the cat has an idea of a mouse rather than an idea of cream. But not
everyoneattributesconceptsto cats,and anywayitis not clear thathavingan
idea of a mouse can be analyzed independently of tendencies to goaldirectedactivitiesinvolvingmice. What seems to me required forthe possibilitythat mice are the cat's real goal is somethingof which the idea of a
mouse is only a special case-namely, an internalmechanismwhich standardly guides mouse-catchingbut not cream-catching.When a process
appropriate to severalends at once has a truegoal, I suggestitis because the
process is produced by an internal mechanism which standardlyguides
pursuit of that goal but not the others. This principle,if correct,has an
important application in biology. Since organisms contain no separate
mechanismsthat distinguishamong the various goals that biological processes achieve, thereis no way of findinga unique goal in relationto which
traitsof organismshave functions.I shall returnto thispointin due course.
With Sommerhoffas amended, then, one can say that organisms are
centersof activitywhichis objectivelydirectedat various goals-for example, survivaland reproduction.Artifacts,by contrast,may or may not be
goal-directedin and of themselves.Thermostatsand guided missilesare;
chairsand fountainpens are not. But we do attributefunctionsto chairsand
fountainpens and to theirparts,and I thinkwe do so by takingthe artifact
togetherwithits purposive human user as a goal-directedsystem.Chairs
have functionsbecause theycontributeto the goal-directedhuman activity
11 Israel Scheffler,"Thoughts on Teleology,"British
Journalfor thePhilosophyof
Science,9 (1959), 265-284.
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CHRISTOPHER BOORSE
of sitting,fountainpens because theycontributeto thegoal-directedhuman
activityof writing.Such objects,whichlack the appropriate organizationto
be independent centersof teleology,mustinherittheirfunctionalfeatures
from people's use of them. In this way we may explain why,as Wright
emphasizes, human intentionsare so central in fixingthe functionsof
artifacts.But at the same time we avoid the false consequence that the
functionof a functionalpart must be known to the user. For the role of
intentionis merelyto determinethe over-allgoal of the use of the artifact.
Once thatis established,the functionof a part is its actual contributionto
this goal regardless of whetherits mode of contributingis understood or
not.
Withthese preliminariesout of the way,we may now statesome analyses
and apply themto examples. I begin withwhatis perhaps the weakestof all
functionalattributions:
X is performingthe functionZ in the G-ing of S at t, means
At t,X is Z-ing and theZ-ing ofX is makinga causal contributionto the
goal G of the goal-directedsystemS.
Two featuresof this proposal require comment. First,it contains five
variablesratherthan two because all functionstatements,weak and strong,
seem to me implicitlyrelativeto system,goal, and time; of thismore later.
Second, I use the progressivetense rather than "performs"because the
latter carries the unwanted implication that the functionis performed
repeatedly or over an appreciable time. Clearly functionsmay be performed only once and by accident. The Bible in the soldier's pocket, for
example, mayperformthefunctionof stoppinga bulletonlyonce. Here the
systemS is soldier plus Bible, and bullet-stoppingcontributesto itsgoals by
saving his life. It sounds false to say: "This Bible performsthe functionof
stoppingbullets,"but the reason is merelythatthe simple presentsuggests
thatthefunctiongetsperformedmore oftenthanithas been. This situation
is worthnoting.Although we give contraryverdictson the two statements,
the contrastdepends on a feature of English verb tenses rather than on
anythingabout theconceptof a function.A good deal of thevariationin our
attitudesto functionstatementsseems similarlyirrelevantto the function
concept. In particular,I shall argue that the contrastbetween weak and
strongfunctionstatementsis solelyan effectof the English articles"a" and
"the."
Mostof Wright'sexamples of usefuleffectsof thingswhichare said notto
be their functionsare stillcases of functionsbeing performed at certain
times. The straynut which falls under the valve-adjustmentscrew and
therebyadjusts a poorly adjusted valve (p. 152) does perform a useful
functionin so doing. It performsthe functionof adjustingthe valve-that
is, it contributesin thatway to the goals of our activitieswiththe car. This
fact, of course, has nothing to do with the intentionsof the owner or
manufacturerconcerningthe nut. As in the brewerycase, intentionsabout
partsare unnecessarygivenintentionsabout the whole. Lehman's bulletin
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WRIGHTON FUNCTIONS
of a drafteeare likewisecases of the performance
the brain12 or the flatffeet
of functions.It is easy to imagine a doctor saying: "This bullet has been
performinga usefulfunctionforyou all theseyears,Mr.Jones ...." On the
other hand, notjust any accidental effectis the performanceof a function.
The accidentalripple in Wright'sconveyorbelt (p. 165) performsno functionifitpasses onlydefectivetransistors.But itdoes performa functionifit
passes onlygood ones, and thatis because itpromotesthegoals forwhichwe
employ the machine.
Now it would be unreasonable to claim against Wrightthat the useful
effectsof all these itemsare in facttheirfunctions-that is, "the functions"
of them. Nevertheless I suggest that the distinctionbetween weak and
strongfunctionstatementsis illusoryto thisextent: there is no important
conceptual constituentof the idea of "thefunction"or "a function"whichis
missingin "performingthe function."To accept our analysisof performing
a functionis to settle the question of what sort of thing a functionisnamely,a contributionto a goal. Whatever"the" or "a" functionof a thing
is, then, it must be at least a contributionto a goal. And I shall now tryto
show thatwhatmore is required fora functionperformedbyX to be among
"the functions"of X is not any fixed general propertybut instead varies
fromcontextto context.
of dividingcases
Initial support for this view comes from the difficulty
thatjustifyweak statementsfromthose thatjustifystrongones. Suppose I
say that although I was never assigned any particularjob on the tenure
committee,myfunctionin the group has been largelyto mediate between
opposing factions.Is thisa functionthatI have merelybeen performing?Or
is it actuallythefunctionof Boorse in the group, a functionthat I have?
It certainly sounds right to say that the function of Boorse has been
veteranlooks back over
largely . . . and so forth.Similarly,ifa battle-weary
a long career in whichhe was shotthirteentimesin the pocketBible, can he
trulysay that stopping bullets has been one of the functionsof the book?
Contraryto Wright'sanalysis, even if he carried the Bible for religious
reasons alone, itis unclearthattheansweris no. And is holdingdown papers
one of the many functionsof my telephone? Again the answer does not
seem to depend on myintentionsin acquiring the telephone, but in some
vague way simplyon how often I use it to do so.
To remove the uncertaintyin thesecases, whatwe need is not to discover
that the itemsin question have some fixed general propertywhich transformsfunctionsperformedintofunctionspossessed. Whatconvertsa functionX performsinto "the functionof X" is our background interestsin the
contextin whichthefunctionstatementis made. Philosophersinfluencedby
Russell tend to forget how often the articles "a" and "the" work in a
context-sensitiveway. Phrases like "the man" and "the book" do not, of
course,assertor presuppose thatthereis exactlyone man or book. Whichof
12
Lehman, op. cit.,p. 14.
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CHRISTOPHER BOORSE
the manymen and books is under referenceis determinedbythecontextof
utterance.Similarcommentsapply to the indefinitearticle.Suppose I say:
"When I walked into the department meeting,a man was quoting from
Chairman Mao." This outrageous fabricationdoes not become true if it
happens thatat the momentI enteredtheroom in Newark,a meetingof the
central committeebegan in Peking. If we apply this point to function
statements,'3the moral is obvious. "The functionof X" willbe simplythat
one among all the functionsperformedbyX whichsatisfieswhateverrelevance conditionsare imposed bythe contextof utterance.In other words:
S with
"The function
ofX isZ" meansthatin somecontextually
definite
system
definite
timeinterval
definite
contextually
goal(s)G,duringsomecontextually
t,
the Z-ingof X is the sole memberof a contextually
circumscribed
class of
functions
beingperformed
duringt byX in the G-ingof X-that is, causal
contributions
to G.
Similarly,somethinglike this will explain "A functionof X is Z":
"A function
ofX is Z" meansthatin somecontextually
definite
goal-directed
definite
timeinterval
system
t,theZ-ingofX falls
S, duringsomecontextually
circumscribed
classof functions
withinsomecontextually
beingperformed
by
X duringt-that is,causalcontributions
to a goal G ofS.
These statementsare not analyses in the sense of two-place synonymy
relations,but forreasonsjust given I doubt thatsuch analysesare possible.
To reinforcethe claim that these formulationsare an adequate general
account of strongfunctionstatements,we maymentionsome of the contextual limitationsby whichwe determinein practicewhat"the functionof X"
or "a functionof X" is. With artifacts,overwhelminglythe most common
limitationis the one Wrightdiscusses: the intentionsof the designer. If one
of the functionsX does or could performis intended by the designer,the
question "What is the functionofX?" is almostinevitablyheard as a request
for thisfunction.But thatis not because we are tryingto trace the etiology
of, say, our automobile. It is because we want to know what good X is for
makingour car run, and the designer is usually the best authorityon how
the artifactworks.Etiologyseems relevantonlyin so faras itis expected to
show how the partcan advance thegoals we pursue withthecar. And as one
would suppose from this explanation, when the presumption that the
designer understandshis mechanismfails,and none of the functionsper13 Notall usesof thedefinite
or indefinite
to context.WhatI
articleare sensitive
isyellow"or
ofX isZ" is notlike"The colorofdaffodils
suggestis that"The function
"The capitalof Maineis Augusta,"butinsteadlike"The qualifications
ofthecandidateareexceptional."
Colorsandcapitalofthings
atanyonetimearefixedproperties
underdiscussion
ofthem;thequalifications
ofa candidatevarywiththeemployment
in thecontext.
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WRIGHTON FUNCTIONS
formedbya partare intendedbyhim,a quite differentcontextuallimitation
comes into play. In that case "the function"of a part will be simplythat
function,if any, which it both regularlyand importantlyperforms.This
situationwas illustratedearlier by brewers'yeast.If ingenious mechanisms
like cars usually resulted from lucky accidents on the part of ignorant
manufacturers,we mightdisregard the intentionsof designersaltogether.
In askingour mechanicforthe functionof thecarburetor,we would thenbe
askingsimplyforwhateveritstandardlycontributesto our goals in driving.
So Wright'sintentionalconventionis no part of the meaning of functional
talk. It is a generallyconvenient contextual device reflectingpart of the
normal background of our discussionsof artifacts-namely, the insightof
theirdesigners-and would disappear if that background changed.
Although much more could be said about the functionsof parts of
I shall now turn to the real payoffof the contextualview-its
artifacts,14
implicationsforbiology.For our analysisdisclosesan ambiguityin biological
functionstatementswhichilluminatessome recentcontroversyin the field.
This ambiguityarises partlybecause biologistssee teleologyon so many
differenttime scales and levels of organization. At one level, individual
organismsare goal-directedsystemswhose behavior contributesto various
goals. By eatinginsects,say,a birdcontributesto itsown survivaland also (a
fortiori)to thesurvivalof the species,but furtherto the survivalofitsgenes,
theequilibriumof theinsectpopulation,and so on. Moreover,unlikethecat
stalkingthe mouse, the bird containsno separate mechanismsreservedfor
each general goal. One can sayonlythatsome ofitsbehaviorservesone goal,
some another,and mostservesall at once. This means thatthereis no sense
in asking whichgoal G is thegoal at which the bird's behavior aims, and in
respectto whichitspartshave functions,except in so faras thisgoal is clear
fromthe contextof discourse.And the individualbird is onlyone systemS.
At the level of a population or species,new goal-directedprocessesseem to
appear-for example, the maintenanceof protectivecolorationin a changing environment15 and one can ascend still higher by viewinga whole
ecosystemas a teleological unit.
The factthata partmayfailtoperform
itsfunction
deserves
someexplanation.
In
is toactivatethe
ofa certainswitch
Wright's
example,one maysaythatthefunction
and thewasherdoes notget
windshield
washer,eventhoughtheswitchis defective
activated.This kindof remarkcan be understoodin at leasttwoways.One might
mean thatactivating
the washeris the intendedfunctionof the switch-i.e.,its
convention
intendedcontribution
toourgoalsin usingthecar.Here theintentional
selectsfromall possiblefunctions
byX thatone whichthedesignerhad
performable
inmind.Or one mightmeanthatactivating
thewasheristhefunction
performed
by
this(kindof)switchin mostcarsof thismodel.In eitherofthesesensesa defective
butatthesametimeone couldrightly
switch
stillhasa function;
denythatithasany
viewthata
thanWright's
current
function.
This explanationseemslessmysterious
purelyintentional
"doing"ofZ byX can playa rolein X's creation.
15 Sommerhoff
on
as an exampleofdirective
correlation
coloration
citesprotective
14
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CHRISTOPHER BOORSE
Given thislatitudeforchoice,whathas happened is thatvarioussubfields
of biology have carved out various slices of the teleological pie and interpreted their function statementsaccordingly. In physiology the goaldirectedsystemS is the individual organismand the relevantgoals itsown
survival and reproduction. Whatever contributesto these goals reliably,
throughouta species or other referenceclass, is assigned a physiological
function.16Thus, although physiological statementsare claims about a
whole class, the goals in question are statesof individual organisms.From
thisstandpointa traitwhichcontributesonlyto othergoals like the survival
of the species-for example, the immolation response of some ants to
fires-will be omittedfromphysiologicaltheory.But such traitsmay very
well be assigned functionsby other biologistswhose systemS is the species
itself.Ecologists create yet another distinctcontext of functionaltalk by
consideringan ecosystemratherthana species as theirunit.In discussingan
analysis verysimilarto our own, Beckner says:
theecosystem
ofa mountain
lake ... isdirectively
organizedwithrespecttothe
biomassratioofpredatorandpreyfishes.
Butwewouldnotsaythata function
of
thetroutistoeatthebluegills,
althoughthisdoesplaya roleintheregulation
of
theratio.17
the level of a species. It seems to me, however,that his definitionsought to have
excluded it. Protectivecoloration is certainlyadaptive-i.e., functional-for each
individualorganismthathas it. To thisextentbiologistsare rightto viewit teleologically.But a species is no more goal-directedtowardmaintainingthisfunctionthan an
ornamental hedge is goal-directedtoward the shape in the gardener's mind. The
hedge also fitsSommerhoff'sdefinitionperfectly:for a range of values of the
gardener's ideal (the coenetic variable) at to,the hedge (by progressivetrimming)
thehedge is notgoal-directedbecause
would come to matchthisideal at t1.Intuitively,
itin no waymodifies
itsbehaviorbetweentoand tj in response to the coeneticvariable.
Each partof itsimplykeeps growingand is or is not trimmedoffbythe gardener.But
the same is true of the species. Each member simply reproduces as usual while
caterpillarsof unsuitablecolor are trimmedby a hungryenvironment.Since space
preventsany explication of what it is for a systemto "modifyits behavior," I will
merelysaythis:if,as I believe,itis wrongto call crypticcolorationor the maintenance
of an ecosystemgoal-directed,then some of the contextsfor functionstatements
mentioned in the text may reflectconfusion among biologists.
16
It is worth noting that since standing states may be causally relevant to the
achievementof goals, relativelyinertparts of organisms(e.g., hair or exoskeletons)
may have functions.Thus, as Wright mentions (p. 152), functionsneed not be
activities.It is also worthnotingthata functionaltraitmustmake a netcontributionto
physiologicalgoals. That is whybreaksin blood vesselswhichlead to theirown repair
(Lehman, op. cit., pp. 14-15), though they activate a function,are not themselves
functional.
A detailed discussion of the relativityof physiologicalfunctionstatementsto a
referenceclass is contained in my"Health as a Theoretical Concept" (forthcoming).
17 Morton Beckner, "Function and Teleology,"Journalof theHistory
of Biology,2
(1969), 156.
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WRIGHTON FUNCTIONS
That, however,is exactlythe sortof thingecologistsdo say.18Our analysis
explains whyitseems naturalto themto sayit. As long as a biologist'staskis
to provide,forsome genuinelygoal-directednaturalsystemS. an operational
explanation -that is,an explanationof howS works-he cannot be faulted
for using functionaltalk. One must simplybe clear about the variables
suppressed in his functionstatements:the systemS, the goals G, and the
time intervalt.
Having thus placed the functionalvocabularyin its broader setting,we
can once again agree withWrightto a limiteddegree. When the biologist,
likea good naturalscientist,is interestednot onlyin how a systemworksbut
also in how it got that way, there will almost certainlybe one or more
functionsof a traitwitha unique claim to be called thefunctionsof the trait.
These functionswillbe the ones thatexplain, via evolutionarytheory,the
trait'sdevelopment. Furthermore,if George Williamsis right,such functionsare invariablycontributionsto one particulargoal-namely, the survivalof the genes thatgovern them.Williamsargues thatthe onlyeffective
evolutionaryforceis the natural selectionof alternativealleles in a Mendelian population; group selection is impotent.19If this is true, then any
group- or ecosystem-relatedfunctionsof a traitmay be completelyworthless in explaining why it is there. For this reason among others Williams
explicitlyproposes a "terminologicalconvention" about function statements:
The designation
of something
as themeansor mechanism
fora certaingoal or
function
or purposewillimplythatthe machinery
involvedwas fashionedby
selectionforthegoal attributed
to it.20
When the question at issue is evolutionaryexplanation,the appropriateness of thisWrightianconventionis apparent. But itis equally apparent that
such a conventionis inappropriateto those otherbiologicalcontextswhere
the aim is an explanation of how some systemcurrentlyachieves the goals it
does. Contraryto Wrightand Williams,there is no reason to force the
physiologistto use "function"in such a way that his statementthat urine
evacuation is a functionof the male urethra could be overthrownby new
evolutionaryevidence. Especiallyin human physiology,the focusof inquiry
is notevolutionat all, but how themechanismcurrentlyoperates and how to
keep it in shape. Similarly,the aim of an ecologistmay be simplyto understand how an equilibriumis in factmaintainedso thatwe can avoid disrupt18 E.g., George L. Clarke,Elements
ofEcology(New York, 1954), definesan ecological niche as "the functionof [an] organismin the community"(p. 468). CliffordB.
Knight,Basic ConceptsofEcology(New York, 1965), calls it "the functionalrole an
organism plays" (p. 171).
19George C. Williams,Adaptationand NaturalSelection(Princeton, 1966).
20
Williams,op. cit.,p. 9.
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CHRISTOPHERBOORSE
ing it. In these contexts talk of functionshas a clear and legitimateuse
withoutany etiologicalimplications.
One can see, then, why Wright'sanalysis so often seems ideal and yet
sustainsso manycounterexamples.To ask for"the function"of a thingis,
indeed, oftento ask forthatfunctionwhichexplains itspresence.The utility
of thisconventionis easy to understand.Witheitherorganismsor artifacts,
mechanismswell adapted to definitegoals do generallyarise not bychance
but by selection.Any importantfunctionsof a part are quite likelyto have
played some role in its origin. Furthermore,etiologicalexplanation is the
onlythingthatinterestssome biologists.In contextswhere theseconsiderationsoperate, Wright'sanalysisseems ideal. But thislinkbetweenfunctions
and etiologyis a featureof "the" ratherthan of "function."By missingthis
point,Wrightmissesthe possibilityof alternativecontextualconventionson
"the" as well as the real contentof the functionconcept. Consequently,his
analysissufferstwo sortsof counterexamples. It failsto account for those
contexts-for example, ordinaryphysiologyor a discussion of brewingwheretheexplanatoryforceof functionstatementsis notetiological.And it
falsely attributes functions-for example, to hornets, gas leaks, and
obesity-where there is no contributionto a goal.
our
Besides preservingWright'ssuccesses and avoiding his difficulties,
context-sensitive
goal analysiseasilymeetshis testsof adequacy. As regards
the term"function"itself,it is completelyunivocal betweenorganismsand
artifacts,thus passing his firsttest.It also distinguishesbetween functions
and accidents:all Wright'scases of accidentaleffectsof thingswhichare not
theirfunctioneitherfailto contributeto a goal or violate relevance conditionsimposed bythecontextof utterance.Finally,our analysisallowsforthe
kind of functionalexplanation Wrighthas in mind whereversuch explanationsare possible. Unlike Wright's,however,itaccounts forthe operational
varietyof functionalexplanation as well and exhibitsa clear connection
betweenstrongand weak functionstatements.Wrighthas made an essential
contributionin statingexplicitdesiderata foran analysisof functionstatementsand in showingthat previous attemptsfail to meet them. But there
seems to be less promisein his own account than in our rehabilitationof the
goal analysis.21
University
ofDelaware
21
of thispaperfromtheDelawareInstitute
for
Supportduringthepreparation
MedicalEducationand Researchand theNationalInstitute
ofMentalHealth(PHS
grant1 R03 MH 24621 OlAl MSM) is gratefully
acknowledged.
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